I had a check engine light come on saying misfire on cylinder one. After having a pretty thorough inspection done the concensus was a bad cylinder one fuel injector so I had that replaced. On the way back home from the shop the check engine light came back on. This time it was that it was running to lean from bank 1. This was from the pre-cat O2 sensor. Soooo, we cleaned the MAF sensor and throttle body, checked for vacuum leaks and replaced the pre-cat O2 sensor. The check engine light came back on after about 15 miles of driving with the same running to lean message. What do you think it is? FYI, 1996 T100 4x4 5 speed.