Recently picked up a 1991 D150 2wd which was originally a 3.9 V6 truck, but now sports a 1990 TBI 5.9 V8. When cold, runs great, however, when warmed up after just a few miles, runs like a bag of marbles! Hesitating and leaning out badly. I noticed the TB temp sensor is disconnected, as well as the O2 sensor, since a bung was not welded into the collector downstream of the header to accomodate it. I know this sounds obvious, but would not having the O2 sensor plugged in cause it to run this poorly?? I would say so, but just want to hear some feedback from you guys. Apparently, the previous owner thought it was fine to not have it connected! Thanks very much!!