Any idea how to stop getting this P0420 code? Just put in a new turbo back exhaust and now I've got this code. It means that the catalyst system efficiency is below the threshold. Obviously due to the newer, bigger piping. But can I cancel out this code somehow?

 

I believe you are going to need a tune.

 

Kinda figured. Thanks man

 

Bit of a funny thing about evos. Two oxygen sensors. Used to verify optimum catalyst efficiency. The idea is to put one before the cat and one after... If you put the cat pipe on backwards you will measure no difference. Woops. Lessons learned. A tip for the other newbies out there.