i closed the hole that was on my down pipe and moved it up in the header then put the bungs in. I am not sure what to tell you man. I am CEL free. Maybe its the OBX design its self...

 

Everything I've read about the OBX for the 3 series is a horror story. The Proto guys fare much better w/them.

 

Yeah well none the less its been a bitch to get it to work right, as far as modification to fit your exhaust. The header itself only comes with one spot for your first o2 sensor which is fine. the second one is past the mod point for making the header fit so the 2nd o2 position still sits in stock piping. No bueno