Cruisin',
Although aggie's post didn't address your specific question and uses questionable terminology (removing weight will not "add" HP but it will improve the power-to-weight ratio, which I think is what aggie was trying to get at), I think your reaction was a bit over the top.
Anyway, weight reduction is a completely valid way to increase the performance of the car without spending a dime. For example, consider removing enough junk from the car to reduce it's weight by, say, 70 pounds. If the engine is stock at 164 HP and the car weighed 2800 pounds before the diet, you've gone from a p/w ratio of 17.07 lbs/hp to 16.64 lbs/hp. That has basically the the same effect as bolting on a part that adds 4.2HP to the "heavy" car. That's the kind of gain you might get with, say, a $180 Hotshot CAI. So by removing 70 pounds of "stuff" - be it interior trim, heavy stereo equipment, spare-tire & jack etc, you've "saved" $180. Plus, the car will corner and brake better.
Parasitic losses can be reduced by installing a lightened flywheel (reduced moment of intertia means quicker RPM changes) and underdrive pulley (reduced speed on the accessories reduces power loss in them.)
Phenolic spacers (do a search for more info) can reduce the temperature of the intake manifold, reducing rarification of the intake charge, increasing power with no low-RPM torque loss.
Aside from these types of mods, you then have to look at airflow modifiers. A CAI, headers, cat-back, throttle body, intake porting etc. Most of these mods are targeted toward increasing high RPM airflow, where small increases in flow rate can result in pretty good HP gains by virtue of the RPM. Most of the changes to get good high RPM airflow result in velocity losses at low RPM, reducing torque. Some thoughts:
- maximize the airflow through the smallest possible runner/tube. A 2.5" cold-air intake might be better than a 3" for lower-RPM torque. Getting headers with smaller primaries may help too.
- leave the VRIS system completely intact. Don't tie them open thinking this will improve power; in fact, tying the #2 plates open will result large low RPM torque loss.