1997 Chevy Silverado sluggish engine

the problem starts when i excellarate to about 70 and start climbing a hill, the engine starts to lose power and the truck starts to slow down as if something is telling the engine to decelirate. It continues to act sluggish even aftre you stop climbing the hill and back off the accelarater. It seems to recet itselfs after I shut off the engine and start it back up. It will then run fine until i ask more off the engine and then it will act sluggish again. have change 2 of the 4 O-two sensors, replaced the mapp sensor, recently replaced the intake manifold gasket. The mechanics want to replace the electronic module next (copmutor), It seems to me that something is telling the electronic module or computor to stop fuel flow to the engine or maybe its adjustment of the timing, what are your thoughts? I have had the catalitic converter checked and appears ok