Don, I've installed the Car Sound cats as part of the UUC Corsa exhaust that goes on our 750iL 6 speed conversion cars. They work great. I think one is good for ~ 350 rated HP, and it'd be my personal choice. We've also got one on the parts runner, a Blazer...Passed emissions with no problems, which is a feat for a neglected, salvaged, rusty 130,000+ mile chevy anything.
best, whit