You've seen the before and after dynos?Really? I've seen some people gain 10whp. Not peak that is. and I think gaining power across the powerband helps more.
Or if you run a blower like you or myself you would see a larger gain as well. But ultimately heads and cams would be the absolute best increase with a TB and plenum. (Thanks to Stal94 for enlightening me on that)You've seen the before and after dynos?
I once heard someone say they saw someone gain 45 rwhp with long-tubes. After getting a little more information, we learned that the car indeed gained 45 rwhp. It was an '03 Cobra that put on long-tubes... and changed a pulley and got a new tune.
A few years ago an engineering student in California did before and after dynos of several TB/Plenum on a stock motor. Accufab did show the biggest gain - 3 rwhp. You can get more than that on built high performance motors.