1998 Chev 2500 loss of power


1998 Chev 2500 4x4 with a 5.7 engine. It has 105k miles.

Problem: Truck intermittently “stalls” as if the engine shut off. The situation: I running at 2500 rpm and then the truck loses its power, I hold the accelerator at the same level, then the truck will “catch” and power is restored, then it does it again. While in the stall mode, the rpm goes up, but now power and speed remains the same or decreases. It appears to do this in high wind and/or long inclines. The truck never mis-fires. This started about 18 months ago and has done it 7 different times. I have replaced the fuel filter, plugs and wires, and had the fuel pump checked (it was okay at the time it was checked). Any help is greatly appreciated. I have Windows XP, PC and use Firefox browser.

thank you. Danny Hill