Boy seems like this could be so many things. Clogged injectors possibly, TPS could be out of adjustment, have you checked the timing and adjusted the valves? Also you could potentially have a vacuum leak somewhere that is robbing you some power. I would check all the hoses and see if there is a vac leak anywhere, then adjust the valves, then check/set the timing. I like to advance mine a little bit more that the 5deg factory setting..like 8 or 10deg.

83 4x4, 3" Lift, 33" Buckshot Mudders