Seems to me there is no solution you can find a problem for.
I am making suggestions and am sharing what I know, it's your job to look into these things and make your own decisions.
By "various levels of boost" I meant that the boost isn't on or off, it depends on the load the engine is under, throttle position etc. I know you say it's only a few milliseconds before full boost but that's not my experience. Eg a car I previously owned (Volvo C30 T5) was tuned to about 20psi but I had a boost gauge and sometimes it would boost to say 10psi and stay there if I was just accelerating moderately in 4th rather than giving it full throttle. The point being if the Mazda is making 8psi I'd assume that sometimes it may only be making 2 or 4 or 6 psi and at each of those points it would need a different amount of fuel.
The lower levels of boost you are talking about is partial throttle, the air flow meter will measure the amount of air the engine is consuming and match it with fuel, it will be less air than an N/A tuned at full throttle. The F2 motor breaths and is real efficient at low RPM's (early torque band) and the vj-11 is a small turbo, you would have to be holding the breaks and giving the car gas or really nursing the pedal in 4th gear (actually looking for that spot in the throttle) for no reason to get the turbo just at the edge of boost.
If you drove the F2T in factory form with a wideband you would see the air fuel ratio's go pig rich in the mid to low 10's when you try tricking the gas pedal into boost, you would also notice the a/r fuel ratio's under boost are really rich all the time from factory, if you didn't have a wideband you would notice gas millage at full throttle and when "tricking the gas pedal" into boost are pretty much the same, you have less fun for the same money.
But none of this matter because it's not about boost, it's about air and the engine gets the most air at wide opened throttle.
The most important A/F ratio's are those at wide opened throttle * the higher the engine rpm the more crucial proper air fuel ratio's become, that is when you don't want the engine to lean out, ever.
At partial throttle the explosions aren't nearly as volatile, A/F's can wander up and down with minimal risk.
So when I mentioned you won't see lower boost level, I was talking about when fueling is most important and the throttles are almost completely or completely opened, tuning is most sensitive and running lean is most dangerous.
You will not see less than set boost with the throttle opened when the engine is getting the most air.
Your other potentially unfounded concern, there are all kinds of ways to set up signal emulators. Life is money or time, want to save a dollar then you spend the time learning and doing, want someone else to do it, spend the money. Because you drive an F2/F2t we can assume you work for your money and aren't wealthy. Do you prefer spending the money you earn or learning and doing it yourself.
RPM: If I simply correct you if your wrong you won't understand and probably wont believe me, If I explain how it works you will understand and you can believe yourself.
F2T target air fuel ratio at full boost 11.8 A/F (low rpm full boost) getting richer to 11.3 A/F (high rpm full boost).
Point 1:
The F2T does run richer as rpm's increase because the time the fuel has to mix with the air gets shorter and shorter, Mazda mapped the car out rich so fuel can cool charge air and has a better chance of mixing with air. I don't know if the amount of fuel delivered remains the same and the amount of air getting in the valves at rpm is smaller (because they are opened for much shorter time) but these motors are happiest (pull hardest) around 11.3a/f at high rpm under full boost, some engines will pull harder leaner than rich but not the F2T, it likes the extra cooling.
So as RPM climb A/F's should get lower in a linear path.
Point 2:
Would you agree that 1 RPM is one full crank rotation and it takes 2 RPM to revolve the cam 360 degrees.
Would you agree that for every 360 degree cam rotation the engine fires each cylinder once. And every 1rpm = 2 spark events on a 4cyl 4stroke.
Would you agree that at 3000rpm the engine is firing 6000 times per minute, at 4500 rpm 9000times and at 6000rpm, 12000times per minute. And that with just those 6 numbers you could easily map out a graft from 100 - 10 000RPM and 200 - 20 000ignitions per minute.
Would you agree that the number of firing events in an engine is a direct representation of how many times each cylinder opens the intake valves and lets in air per minute based on rpm.
And that this graft also represents the number of breaths the engine take per engine.
And that when you double the RPM's you cut the time the valves are opened for in half.
Injectors are rated in CC/ML per minute (lb/hr) and duty cycle represents how much time they spend opened during that minute, so a 200cc per minute injector firing at 50% duty cycle would deliver 100cc per minute, 25cc/15seconds...
The faster the valve cycles are the less time the injectors have to deliver fuel and the higher the duty cycle must be to deliver the same amount of fuel for each breath of air.
Wait! does this mean the injectors try to deliver the same amount of fuel to each cylinder for every time it fires regardless of RPM and that if you double the rpm you double the engines fuel requirements?
Armed with this simple bit of knowledge, designers of extra injector controllers know exactly how to map out the extra injector controllers fuel deliver, the map curve always stays the same, you just set the boost/vacuum start point based on when you need extra fuel and you set the gain (starting duty cycle). Replace "Firing events per minute" Fuel requirement per minute. Now the three red dot's represent same "Gain" setting at 3 different RPM, you could dial the gain in at 4500 and the injectors will meet the dot at 6000rpm or vice versa.
Because * always make sure the near red line A/F's are right or adjust the gain accordingly.
The Extra injector controller delivers fuel to all four cylinders before the throttle body making it much easier to make a universal map for any size injector because they deliver over 360*.
Individual port injectors are set up the same way (follow the same map) but in batch fired 2X2 injectors each fire every 180*, single fire injectors fire once every 360*. When they start opening, how long they inject for (# of degrees) and how much fuel they deliver all need to be dialed in.
But this only makes sense if the amount of fuel required increased at exactly the same rate as RPMs which I can't see being the case.
Can you see it now?
(no offense but this is a question you could have answered with a bit of searching, thinking and common sense).
The extra injector controller also follows the map sensor voltage 0-5V signal it receives and increases the fuel as voltage increases. So if my controller is set to come on at 15psi and I set my manual boost controller to 21 psi and set the gain to say 25% and A/F's are perfect from spool up to redline then I turn the boost down to 17psi or up to 22psi the A/F's will stay the same.
If the black line on the graft represents fuel delivery at 17psi the red line would be fuel delivery at the same gain but higher boost, say 20psi:
2. You said in a previous post
"You can run different rate or adjustable rate FMU in place or the fuel pressure regulator and dial in 7psi boost on the factory N/A injectors with higher fuel pressure and a wideband."
Is there any reason this by itself can't be the solution? Runing an adjustable fuel pressure regulator could effectively increase the fuel delivered through the NA injectors, solving the whole problem?
Yes but this would ignore rpm and you would have to set A/F's for 11.3 at high rpm, they would likely be 11.3 or richer at lower rpm .
Running higher fuel rail pressure whenever your on boost would tax the factory fuel pump, a high volume, high pressure pump would be required.
There is a 2nd dilemma, say you get a 6:1 or 12:1 or whatever FMU and 6:1 or 12:1 fuel rail pressure to psi signal isn't enough with base fuel rail pressure set factory (34-40psi) your only option is to increase base fuel pressure and be rich all the time to get the right peak boost, peak rpm air fuel ratios.
3. I was doing some research into options and came across this one - not sure if you're familiar with this approach but would be interested in hearing thoughts.
AutoSpeed - Electronic Fuel Pressure Increase
It may not be any less work but I feel like it's at least worth considering.
That is pretty sketchy and if I read this correctly :
"When the electronic switch is activating at the right time, wire the solenoid to the on-board relay so that as the switch clicks over, the solenoid closes. (Full wiring instructions for switching things is covered in the kit instructions.) "
The kit uses a normally opened solenoid valve, so if the relay, control board switch, solenoid valve or connections fail, the solenoid valve stays opened, fuel pressure stays factory and you need a new motor.
That is a lot of faith to put into cheap controller with flimsy screw down wire connectors that often loose grip of the wire.
I also don't think this kits for forced induction vehicles, the N/A and GT have a 1:1 rising rate regulator, for every one PSI of boost pressure from the vacuum port the regulator gets fuel rail pressure is increased by 1psi.
This is to make up for the pressure inside the intake manifold, if fuel pressure is 40ps and boost is10psi the injectors will deliver fuel at a 30psi fuel rail pressure.
Because his kit uses a ball valve to regulate high fuel pressure, it's a fixed fuel pressure rate from the time the solenoid valve closes and the factory 1:1 FPR wont change fuel pressure because the pressure is higher after the FPR.
Years ago I came up with an Idea for something similar for the F2T to go above 15psi on factory injectors.
This set up has failsafes, the solenoid valves is normally closed so if the pressure switch, relay, solenoid or wiring fails fuel pressure stays higher and the engine will run richer at cruise and idle but doesn't blow up.
This would be the best way to run a FMU without ending up rich at idle and cruise.
The FMU would vary fuel pressure based on boost to fuel pressure ratio and because of the pressure switch/solenoid valve never effect boost a/f's below a certain boost allowing to dial in initial fuel rail pressure and the effects boost pressure has on increasing the fuel delivery when extra fuel is needed.
Doing this on factory injectors will only get you so far, even with a high pressure high volume pump there is a limit to how much pressure the injectors can close under and the fuel system can handle.
You could run slightly larger than factory injectors and lower idle fuel pressure to correct idle and cruise a/f's, I wouldn't run a fuel rail pressure below 25psi at idle, the adjustable 1:1 FPR's I run default to 40psi at atmosphere (vacuum hose off) no matter where they are set bellow that at idle vacuum, or you can adjust the screw with the vacuum port off and eventually raise pressure above 40psi at atmosphere and it will stay high at idle.
All that is needed is a performance fuel pump, 4 high impedance injectors that fit in the fuel rail that are close enough in size to factory to deliver factory fuel amount at 25psi (minimum) fuel rail pressure (injector calculators online will calculate this) and fit the F2 fuel rail, an adjustable fuel 1:1 fuel pressure regulator, a fuel management unit, solenoid valve, relay, pressure switch, hose, some T's, hose clamps, a wideband, some math, trial and error and luck to dial in how many psi rail pressure is required per extra psi boost.
All that and you might get an okay fuel A/F curve with spots (like atmosphere pressure) the engine is to rich.
You can't increase injector size beyond this point without idle cruise issues and are limited to maximum safe fuel rail pressure on slightly larger injectors as your peak fuel delivery.
An extra injector controller cost less, delivers better fuel maps, cools charge air and completely vaporizes with the fuel in the intake manifold and when you run out of injectors adding mods and running more boost, just install larger ones and turn down the gain.
------------------------------------------------------------------
I say:
-Speeduino is your most versatile option, one of the most affordable and a lot of work.
-An extra injector controller is the second best way to regulate fuel in boost, the other of the most affordable solution and the least work.
-An injector emulator and extra injector set up properly with a bit of AFM tweaking can offer a good A/F curve because it will follow the ECU's injector duty cycle.
-An FMU would be the second most work, most expensive and yield the worst A/F curve.
-The "autospeed electric fuel pressure increase" will blow up your motor.