During hard acceleration, I notice a bad rotten egg smell. I think I may have a bad cat. If it is, I wanna get a magnaflow high flow cat. My question is, will they make my exhaust louder (Which I dont want) and will they pass emissions in NY

 

If you don't get a check-engine light, I'd assume your cat is still OK. OBD-2 rear oxygen sensor's job is to measure the cat's performance. Rotten-egg smell is sulfur, which isn't really the cat's job anyway.

 

try using a different brand of gasoline and see if it makes a difference.. i know it's a simple suggestion but give it a shot.. It could be the battery..