There's a bit of mis-information in this thread. Some companies make a down pipe that includes the mid pipe and some are 2 piece systems. The bottle neck occurs in the DP/MP sections. (also known as mid pipe, test pipe, or race pipe.) The 02 sensors are in the DP section so the test/race pipe replacement won't throw a CEL. Running the DP/RP with the stock CBE (cat back exhaust) eliminates most of the bottleneck (after the turbo) and will add most of the power that you can get. Adding a CBE won't net much more power since the stock system is pretty free flowing on it's own. I run a DP/RP with the diode cheater fix with no CEL's, no smoke. The stock CBE has a resonator and a muffler, it does not have a catalytic converter. There are 2 cat's one in the DP (down pipe) and one in the MP (mid pipe.) Some have tried the 02 bung extender cheater fix but it doesn't seem to work for everyone. That fix goes on the secondary 02 sensor, (not the one closest to the turbo, the one that's downstream of the first sensor.) I have 4k miles on my set up with the diode trick and like I said no CEL. Sorry if some of you know the terminology but it was clear some of you don't know what parts your referring to... if you get under the car and look it should become clear exactly what your looking at.
