Should I replace my catalytic converter since I have to replace the muffler anyways? My muffler was completely knocked off from a nasty parking barrier that snuck up behind me so I need to put on a new one and I was thinking of a cool sounding one like thrush dual output or something like this. If I have to get the work done by a mechanic js it a good idea to replace the catalytic converter at the same time and will it increase horsepower at all?

Depends on how old your cat is. Your not going to really add HP with a new cat, but you will get back what has been lost over time.

sorry about my lack of forward info. I own a 99 sse that is all stock except for one front right rim that is now from a grand-am. I have the interlaced bronze on aluminum original rims but one got busted from a nasty curb that happened to be hungry for aluminum one night. I looked but couldn't find a replacement so i went with a rim that fit.