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A blocked injector is a possibility though unlikely IMHO.

There are a number of possible causes for what you describe:

Plug wires on these cars are notorious for short life spans.

Oil in the plug wells can cause misfires and rough running.

Dirty or clogged fuel filter can cause fuel starvation problems.

Defective VAF sensor can cause problems you describe.

The first three are pretty easy to fix yourself. Buy some NGK wires from your Mazda dealer and some new plugs while you are there. If you find oil in the plug wells, dry up as much as you can and consider having the valve cover gaskets replaced soon. A fuel filter is a bit tricker and requires caution (fuel under sure to release the system pressure before changing it) but can be done by yourself.

A VAF sensor is a bit harder to diagnose. You can check the sliding core to ensure it slides easily without binding or sticking. You can use a voltmeter to probe the outputs (see my web site under Malf Codes, code 08 for wiring details) to look for 4.00V closed, 0.35V open and a smooth transition between these two points.

As for the TPS, it's used largely for three purposes. One, its idle-switch tells the PCM when the throttle is closed and is used for idle and DFCO (decel fuel cut) strategies. Two, the throttle angle (expressed as a percent of WOT) is combined with RPM and VAF readings to get engine loading, used for fuel and spark. Third, the rate at which the TPS is opening tells the PCM how much enrichment is required (to mimic a carburetor's acceleration pump) to prevent bogging due to tip-in.

From the perspective of adjustment, getting the idle-switch right is paramount. Everything after that comes "naturally" from the way the sensor is constructed.

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