Just bought a 2000 Venetian Red R with 120k. It has been throwing the P0422 code which, from what I hear, could be any number of things. I found out post-purchase the car has an aftermarket 3" DP (& Cat) on it. Could this be the cause? I also noticed that when running, the exhaust temperatures are quite different between the two tips, although there is still airflow from each (one is significantly warmer than the other???). I hear the Cats break down inside after a while and I was thinking maybe something got a bit plugged up and may be causing the code and differing exhaust tip temps. What does everyone think?