sounds like your cat is clogged. thats what my car was doin. when you go wot your putting a lot of pressure on the exhaust, and if your cats clogged, the exhaust cant go anywhere, which will make your car misfire. and if the cat is clogged, the rear o2 cannot get a proper reading, which is why you have that code. my suggestion is order an off road 3" dp from zzp and put it on. all depends on if you need to pass emissions.