After letting a mechanic friend look at it he says I should replace the cat soon. What should I replace it with? I'm tempted to have the exhaust redone at the same time but I don't want to spend the whole bank How much should I expect for a cat replacement? I've been reading here that the rest of the exhaust should be around $200? Any recommendations? I don't need loud or deep as I am happy with the current sound. Is it bad to just replace the cat and not the rest?