Hello i have a 02
A4 1.8t and my CEL came on and the code says it was for my cat i put some kind of cat cleaner that you put in your gas tank i was woundering if anyone had any luck with that kind of stuff and what could of made this happen i dont smell that bad smell when i drive so i really never knew anything was going bad but my CEL has been on for awhile.. also woundering if putting a test pipe with a stock exhaust would be somthing to look into... thanks for the help...i also have about 85,000 on it