A few weeks ago I posted that my cel came on and gave me a P0420 code. Got some feedback but a new question has come up. Awhile back (four years ago) I had a custom exhaust put on from the cat back. Where the pipe is suppose to split into a y, the guy t"d it off. It went from a 2.5 inch pipe to 3 inch t then back to the 2.5 inch pipe to the mufflers. One, would this hamper the performance of the car. And two would this clog the cat. quicker causing the code to come on? Thanks.
