My new O2 sensors are already on the way, but just wanted to get any other opinions out there. Right now, I am pretty sure that one of my O2 sensors are just bad, and that is also what my tuner is thinking as well. I am running e85 and comp stage 3 cams. Pretty much, my driver side upstream oxygen sensor is not sweeping. Even when the afr is right where it should be. There are no vacuum leaks or such. Does anyone think that the O2 might not be the problem?