I had recently gotten a obdII code for something about catylist so im assuming my converter on the exhaust is screwed somehow. Does anyone know how much OEM replacements are? Also, i also happened to notice this long cylindrical lookin thing resembling a glasspack on the exhaust. I was told it was some sort of resonator. can anyone tell me exactly what it is called, what its purpose is on the exhaust system and would it hurt the fuel economy or performance at all if i have it removed? Im wanting a little more sound out it and im not able to sacrifice alot of money.

Before you buy an OEM replacement, read this: Advisory for All '01-'02 Grand Prix with SII 3800 Engine Concerning CAT Converter

If you have to buy one, one option would be to get a Magnaflow 23405 and have it installed. (You'll need to supply gaskets and bolts)

That glasspack-like device is a resonator. It removes drone and rasp from your exhaust note. On a completely stock system you can remove it and get some more sound. However, once you delve into headers and such, you'll be wanting one back (aftermarket exhaust or no).

A couple of Summit Racing street and strip muffles would do a good job of adding some more sound. Leave the resonator alone if you go this route.