Quick back story here... i bought the car with out a catalytic converter. It had a test pipe in its place. Went back to dealership and they gave me a brand new cat. But now its throwing a code.. dont know what that code is but as soon as it came on i switched it back and it went away. Any ideas of to why it would throw a code with a cat and not one with out it? Thanks! Oh and i ask them how they didnt notice it when the smog test or whatever test they do and they said the sniffer test never picked anything up so they never looked.