I have a 89 1/2 ton GMC with the 4.3 2wd. I barley ever drive it but resently it has got a hesitation in it when I want to give it gas. I stuck some fule injection cleaner in there and it did not seem to help. I am leaning toward it being the fule pump, reason for my conclusion is it runs fine when I start it up and run a few miles but as soon as it heats up good I start to get the delay. To best describe it say im in 4th gear and I hit the gas it putt putt putt... then kicks in. It deffinitly seems like a fule problem not getting to the engen steady. Anyone agree with me or have any other ideas id love to hear em, the fule pump in these are on the top of the fuel tank and not really an easy fix.