Originally Posted by
avguy
Let's back up just a bit. First, what year and mileage? Cats have long-term warranties, which may come into play here. Next, who is telling you it's a bad cat, and how did they determine that? Was the CEL on, and codes read? (if so please list all codes). Has this Aveo been misfiring, and if so, has it been going on for a while? Any repairs or maintenance done recently? Last question (for now), what's the condition of the exhaust system (all pipes and muffler)? Lots of rust may factor into whatever decision you make (assuming it's actually a cat problem).