i have no cat right now. i'm going to get my headers put on for 100 to have a y-pipe bent with no cat or 150 to put in a punched out cat. i want to have at least a punched out cat(just has to be there for inspection) but i was wondering how much performance if any i will lose from a aftermarket cat like a catco or something. its going to be in a 3" exhaust with a flowmaster 80 muffler.

 

You will lose nothing at all, even if you don't punch out the cat. Modern high-flow cats might as well be a piece of straight pipe. You can look right through them; they're a honeycomb material, made such that the gas flows straight through the cells.

It's a wise idea to put one on there. Even though some areas of the country are eliminating emissions inspection, a whole lot more are adding it; and it's alot cheaper and easier to deal with it before you've already spent money on something else, and then get forced to do it at the last possible minute along with everybody else that wasn't prepared.

 

will the sound change much with a high flow cat? i heard flowmasters sound better with a cat also because of the waves hitting the baffles without a cat. is that true? my brother has a 97 z28 with the dual cats and a flowmaster 80 and it has more of a mellow rumble. its still loud but not quite as loud as mine and mine has 4x24" tips and its more raspy. i know the lt1 is a lot different than mine but would it sound more like that?

 

Mine has the same sounds with or without the cat although it is louder without the converter.

 

The catalytic converter acts somewhat as a resonator. It reduces exhaust sound at all RPM's it seems.

I say put on an aftermarket high flow cat. It's really not doing any harm to your horsepower numbers and you have the cat there in case there's some sort of inspection that may be necessary at any time.