Backfires, wont excelerate

The truck has a bit of a starting problem, the head gasket was replaced recently, the air intake sensor dosnt seem to work, but works when we cut one of the wires on it. The truck starts okay and idles great. The tank had dirty gas so I replaced it, new tank and filter, and now it wont drive properly. I had switched out three filters in the last few months, so it seemed to be a fuel problem, because the truck would run fine, once I replaced the fuel filter. If I try full throttle it cuts out and backfires, nothing, then sometimes it kicks in and I can go around 40mph and then backfire and no throttle. When im in neutral, it seems I can get the revs up a bit, but not much. Any ideas.