I've been reading lots of articles that are pointing to an interesting trend in N/A buildups. Upgrades that do more harm then good. And I am not talking about crappy products either. Nismo, mugen? I think the problem is that cars are being designed so efficiently, that there isn't much room left for improvement in these N/A engines.
Case #1: Dyno shootout of Celica GT-S cat-back exhausts. Average gain of just 3hp, with a reduction in power below 5,000 rpms in almost all cases. One exhaust managed 5hp.
Case #2: Mugen S2000. Super expensive carbon-fiber intake, stainless headers, and steel/titanium cat back exhaust. Probably $2,000 for this stuff, and NO GAIN in power. Whats worse, it actually lost about 5hp from idle to 6000 rpms. But it sounds good.
Case #3: Nismo R-tune 350z. Nismo Cat-back, Nismo headers, Nismo CAI, Nismo Cams. $4,300 in parts (Nismo is a rip-off) plus 20+ hours of labor (another $1,000?). Net result is a claimed 23whp, although on 91 octane gas SCC only saw 10whp gain.
Weak fellas, weak. Forced induction is better. A $400 reflash on a WRX could get you the same gains as the Nismo, and obviously just about anything can not improve performance.