Problem with tuning my procharged mustang and the a/f gauge reads really lean. The car used to run pig rich about a month ago and now it reads lean. Running a car too rich would cause an O2 sensor to go out right? I have plenty of fuel pressure. The real time data from my O2s read for upstream 1 to be .3 and upstream 2 to be .9. Does this mean upstream O2 is bad? thanks
