would putting a muffler in place of the cat do any thing detrimental? i dont know how big of a muffler you could find to fit there, but i wanna quiet my car some and i dont want to cut up my loudmouth if at all possible. just want to see what you guys think

 

Cats actually do a fair bit of muffling themselves, so considering the size, I doubt a muffler the same size would change the sound level much. I'm assuming this is a single cat exhaust. Theres no way you'd get a muffler to bolt up to each manifold and actually fit on a dual cat car.

Why not just put a longer resonator on your LM? Or better yet, trade my LS1 SS catback for your LM!

 

Might want to provide some specifics on your car - year, model, engine, tranny and any major mods. Why not use the "Signature" field, to provide this info, so its always available and included in your posts?

With my Y-pipe exhaust system, I wanted to run cats on the street to pass NJ's rigid inspection/emissions requirements, but be able to drop out the cats for the track when running highly leaded racing fuel on a 300-shot of nitrous. Catback was a 4" Mufflex system. I bought a pair of Borla 3" XR1 racing mufflers, and a pair of 3" CarSound cats. The guys at Mufflex made up a Y-pipe that would accept either the cats or the mufflers, with bolted flanges for quick replacement. There was no detrimental affect on performance.

The Borlas also kept the sound level down a bit on the street, when I didn't want to put the cats back on.