1997 Chevy Cheyenne hesitating during acceleration

1997 Chevy Cheyenne mileage: 106,000. I first noticed that it was hesitating during acceleration, and that it was "bucking" while driving down the road. I thought the fuel pump had gone week, so I replaced it. While this helped, the problem persisted. I gave it a full tune up, wire, cap and rotor, plugs, fuel filter, and it was all done with factory parts. All of my hoses are tight, and the only thing I can think of that is left, is either a compression problem, which I doubt seeing as it came on suddenly, and not gradually with time, or the EGR valve, which as far as I can tell is still working properly. I have tried an injector cleaner, and nothing. I reviewed the FAQ's, but none of them seemed to specify my persisting problem. What do you think the problem could be? I have been working on this truck, making it perfect, for way too long to let this stop me.