I'm thinking of having my precats removed from my downpipes. Seems like there would be some obvious performance increases, not to mention increased turbo life. I'm wondering what would be the downsides to this? (besides cost...) I know there's an O2 sensor in there that I would lose, resulting in DTC's. I have an APR ECMS ECU that can clear DTC's but I still don't want to have to send it to them for the downpipe programming. If I keep the chip like it is now, would the ECU eventually react badly to the continuous DTC's and go into limp mode or something? Also, I know the MTM state III kits comes with a 5bar fuel pressure regulator and special spark plugs. Would I need something like this as well with this setup? And does anyone know if the APR downpipe programming does anything besides ignoring the missing O2 sensor? Sorry about all the questions. Anyone out there with knowledge of this subject would be greatly appreciated!

While it may be possible to write out the O2 sensors in the program, it would be far better to make a filler pipe(s) with the O2 sensor still in them.