Yeah thats what im trying to get at, Your rear 02s don't have anything to do with AFR so even if you jacked them up it should not make much of a difference.
Ding ding... I missed that part when I read the OP. If an injector was dropped or something, it could very well be fubar. I would install your old ones and send those off to be flow checked cleaned and tuned. Then sell them with the data card that you get back with them after they are checked and/or fixed. Some will pay a bit more just to have a known flow on injectors. You would be surprised at how different one injector can flow from the next. Especially after some miles have been put on them.
Also are you sure that isn't false knock your getting from something like the exhaust hitting something? false knock usually shows up at high RPM on WOT pulls.