Offroad H-pipes (no cats) are pretty loud, even with stock mufflers, but if you get a pipe with the high-flow cats (like I plan on doing) it will not be nearly as loud. Plus you will still gain about 20 hp. As far as the check engine light coming on, running an offroad pipe WILL cause the light to come on (speaking from experience). I have heard that the high-flow cat versions will not set the light. H-pipes also work well with Flowmasters. I will probably get the MAC high-flow cat H-pipe and 3-chamber flows. That combination should sound/perform pretty sweet!
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'97 Cobra, MAC Cold Air Kit, 3.73s, Rio Red
[This message has been edited by King Snake (edited 11-26-2000).]