The whole point of modding a car is to measurably increase performance and that is tougher on a Porsche because those crazy Germans already did a pretty good job. Just bolting on sexy parts won't get it done. We need independent measurement and verification to separate legit gains from the BS, and get beyond the marketing hype which is pretty rampant.
All of this 986 stuff was tested extensively about 20 years ago and the results were interesting and often disappointing. Aftermarket products failed to meet their claimed HP improvements across the board. Fabspeed makes sexy products and their exhaust is arguably the best looking and best sounding of all aftermarket exhausts. They claimed a 22hp bolt-on gain but independent testing showed the stock exhaust actually made more power with a fatter torque curve. They claimed a 15hp gain with the EVO intake but independent testing showed -3hp and higher intake temps.
Underdrive pulley- Verified 3-5hp gain to the wheels across the RPM range by reducing parasitic drag.
Weight loss- Verified improvements in acceleration, braking, and cornering.
Plenum- Combined with TB, exhaust, and custom software tuning- 10-15hp depending on model with more improvement on the 3.2L.
Airbox- 987 box performed the best gaining 1-2hp on 3.2L
If we are serious about improving performance we need to do the math, and before and after testing to confirm that gains are real and not just marketing BS.
In an earlier life, we used to hot rod Ford, Chevy, and Honda motors to race at the drag strip and off road. Detroit mfg tolerances were pretty loose then with a lot of internal friction and you could make 30hp verified simply with a balance and blueprint, getting everything up to the engineering specs. Add a real intake manifold, Holley carb and custom exhaust instead of those stamped things from Detroit and there might be another 30hp verified as we allowed all that displacement to measurably breathe better. Porsche doesn't miss much, tolerances are a lot tighter, and we have to get more creative to squeeze more power from these well-tuned little mills.
Tuning is fun as long as you independently measure and verify gains along the way. This requires regular visits to a fairly precise dyno. Trusting aftermarket marketing hype is a fools errand and leads to disappointment.
These guys did a pretty good study on Boxster tuning and they did significant before and after testing along the way. A few interesting findings: They did not find improvements with an underdrive pulley as many other's have seen and verified. Also the stage 1 ECU remap caused the power to be down 10 hp vs the stock ECU tune on their modded car with a rich AFR. A custom dyno tune would probably deliver more juice if they got the AFR really dialed in.
https://www.youtube.com/watch?v=kja5LSsUT_g