I replaced my BPM exhaust setup for a Greddy Ti-C (non-resonated, catless, no-taper) last night and due to the lack of a bung on both the downpipe and exhaust, I was not able to reinstall the 02 sensor so I just unplugged it. Now I know the car will throw a CEL due to this but tonight I did a WOT pull since the install and the car feels sluggish. Is this a result of the 02 sensor not being present? To my understanding, the only real purpose of the rear 02 sensor is to make sure the catalyst is doing it's job? Am I right or wrong? Would this cause the car to go into "limp" mode? I must note that I had to disconnect the battery so we could "extend" the length of the downpipe as it is a little shorter than the factory downpipe. I'm going to reupload my tune to the car to see if maybe it just needs to be reflashed due to th battery being disconnected for a decent amount of time (~1.5-2 hrs).