I think the cat is broke, I get a rattle sound from exhaust area now. Went away for a minute but came back... got pretty bad, was rattling when I rev engine. Didn't have it inspected by the muffler shop yet but I'm pretty sure thats what it is. I dont have the money now but when I have to fix it should I get an upgrade? What do you suggest, I have borla exhaust. I believe everything else is stock.