do you have an offroad x-pipe? (no cats). If so you need MIL ELIMINATORS, or a tuner to shut the rear o2 sensors off. I had the same problem but now its fixed thanks to the tuner.
A forum community dedicated to Ford Mustang owners and enthusiasts. Come join the discussion about performance, builds, modifications, reviews, engine swaps, classifieds, troubleshooting, maintenance, and more!