Hi,
So ive been running a catless obx full race header in my 04 ep3 for about a year and a half with no issues. I have 2 anti-foulers in place to keep the CEL from coming on but last week I took the header down to re-wrap it since the old stuff was disintegrating pretty bad and falling off.

I re-wrapped the header and re-installed it and now I am getting the P0137 code which is for low voltage for bank 1 sensor 2 (rear o2 sensor). I looked @ the data in the scan tool and it is showing zero volts at idle and it will only register any voltage if i really step on it. I replaced the o2 sensor before even looking at any of this and it still is a problem. I even installed the o2 sensor without the anti-foulers and while it does read the voltage properly I get the P0420 code for a bad cat.

I tried using one spacer and drilled it out to get more flow onto the probe but it still removes it too far away from the exhaust stream. the weather recently got a bit colder as well but i dont think that would make a difference when it comes to the exhaust flow.

i am going to try shortening one of the anti-foulers some more but i am not sure that will work either.

Does anyone have any ideas?