[mbtoloczko]

My car was the same as yours, and I was also a bit disappointed. However, the specs on the SVX say that peak power is at 5500 rpm, so perhaps it shouldn't be so surprising that power drops off after 5500 rpm.

I've tried a bunch of different exhaust configurations, and none of them ever made a significant change in the position of the HP peak.

Assuming that you want the reflected exhaust pulse to come back to the exhaust valve at about 180-200 deg after the exhaust valve opens, then for sonic wave scavenging at 5500 rpm, a reflector is needed at about 54-60" from the exhaust valve (if the speed of sound is about 1500 fps). This is the location of the factory 3rd cat on a US SVX. If you look at my last exhaust system before I sold my SVX (see "custom exhaust 2004" in my locker), I ran single 1.75" ID pipes to that location and then put two 2.5" ID tube mufflers at that location. If anything was going to improve scavenging at 5500-6000 rpm, that would have done it, but you can see that the HP/TQ really isn't much different than any of my other 5MT HP/TQ curves.

IMHO, the 5500 rpm peak power with a stock motor is controlled more by the cams and not by the MAF maxing out. If you look at a few of my LM-1 data logs in my locker (see tuning data) where I measured the MAF voltage with the MAF bypass installed, first you'll see that the MAF voltage never reaches the 4.8 V limit that the MAF can produce, so the MAF is not maxing out. Second, you'll see that the voltage reachs its peak at about 5500 rpm which is right where peak power is made.

I think that if you want more high rpm power, cams are needed. However, the MAF is not far from maxing out, so either a MAF bypass or Stage II MAF is needed to realize the effect of the cams. With that said, I don't have an explanation for why other people's cars pull strong after 5500 rpm. I'd like to see dyno curves, MAF signal voltages, and AFR values for those cars. It would be useful in making sense of everything.