CEL Code P0420, Please Help Me Resolve It
So two weeks ago, my CEL came on while I was driving rather tamely. I took it to an exhaust shop, because I figured the light was probably due to a leak. They pulled the code P0420, "Catalyst System Efficiency Below Threshold (Bank 1)." They said there were no leaks and that the catalyst must have failed and I should replace it. I told them to reset the code and I would see what happened.
Yesterday the light came back on, and I am sure it is the same code (although I will have it checked later today). I have Comptech Headers, an RT Cat, and a Comptech Cat-Back. I'm currently at 35k miles and all of those parts have been on since 3k miles. Is there really a chance that they just suddenly went bad? I have never had a CEL before so I'm not sure why it would start now.
I know I could just get a non-fouler to trick the O2 sensor, but I am worried that there is something actually wrong with the car. The reason for this being that I have been getting worse gas mileage than historically and my engine has been noisy at idle and certain RPMs. Any ideas as to what else might be causing this?
I don't want to just take the car to the shop and say "I think something is wrong" because they will come up with some marvelous reason for me to shell out a grand.