I have a 93 SOHC, and a long while ago I got a universal muffler put on. Its basically a 2.5" diameter tube with no hindrance in the pipe at all. I noticed that it gave a lil more pull in the low RPM range, up to bout 3500rpm... but from 4500 on it seems like my engine is completely robbed of power. Can a muffler do this... or does the engine just not have to power in that range?