The Jimmy is surging especially when I shift it into 2nd gear and run in around 2000 to 2500 rpm. If I hold the speed steady it gets a slow surge in the forward motion of the truck. I don't hear the engine surge or the rpm just the vehicle, sort of like hitting a bunch of small puddles one after the other on the road making the truck slow for a second and then regain speed again. I also noticed that it sort of sounds like it is back firing or missing internally in the engine at a little higher rpm in 2nd. A little history on the truck: New plugs, wires, cap and rotor a couple months ago rebuilt fuel pressure regulator, fuel pump, and fuel filter New tranny 2 years ago and 25,000 miles ago, GM brand new 700R4 with newly rebuilt 10 bolt rear with gov/loc and 3.73 gears. Also when cruising at highway speeds around 70 mph the truck seems to have a problem staying at speed. I have to nudge the peddle up a little more to keep it at the constant speed, almost like the truck is dragging or having trouble holding the power needed to keep the truck going. I'm not sure if this is a transmission problem or fuel/ignition area. Any help and ideas would be appreciated to get the beast up to par again. I'm at a loss and wits end.