2000 GMC Sonoma Question: Any ideas why my truck would accelerate when the AC is turned off?

While driving the truck became sluggish and then died altogether. Was able to diagnose it as the fuel pump. Replaced it and then a whole slew of other issues cropped up. Was choking out and also accelerating on its own. Got the codes read and replaced the throttle position sensor. Also changed plugs. The choking out issue seems resolved but now the heat won't work (which it was previously......only blows cold). I have determined that the truck accelerates (up to 16mph with the rpm around 1700) while the AC is off without ever touching the pedal. Turn the AC on and idles normally. I could actually speed up by turning the AC off. I was able to locate some wires that were damaged by the manifold but there were no breaks and I insulated them. Anybody got a clue???