I have a 1994 Chevrolet Z-71, 350 V-8, Automatic. I started having trouble with it missing. I just made a 500 mile trip and was wondering if I was going to make it home. The truck misses terribly and backfires through the air cleaner. I noticed the truck was only running 100 deg. on the temp gauge so I changed the thermostat on the road. Mistake. It made matters worse. The truck runs fine at 65 MPH +. It won't hardly run at all at low speeds. I went to the local NAPA and was told by the local "expert" that it was either a tempature control sensor or a knock sensor. I tried the $8 option and put the tempature control sensor on. No luck. Does anyone have any idea what is wrong? Do you think it is the knock sensor? I hate to invest another $55 for nothing. When the truck misses badly if I floor it, it will smooth out. Any help would be appreciated. I did a code scan by jumping the A&B terminals under the steering column. It flashed a 15, 22, and a 44.

Well for starters when is the last time you did any maintenance such as fuel filter, spark plugs AND wires, cleaned the injectors. I am laening towards possibly a spark issue, low rpm = weaker spark and running crappy, higher rpm = stronger spark and it runs better. Just a thought and a place to start.