I have a 85 k5 6.2l diesel ex military truck with 39,xxx miles that I've been daily driving for about a year with no problems. Ive converted it to a 12 volt system and put new glow plug in it when i got it. The other day on my way home from work the truck had little power and it started to hesitate at higher rpm and wouldn't shift unless I lifted off the throttle. To me it felt like it was running out of fuel. I changed the fuel filter and lift pump already, made sure I had no contamination in the fuel, and made sure the air filter was clean. I'm hoping that its not the injection pump but I'm running out of options. Does anybody have any suggestions on other thinks it could be? I've been searching around this site and others for 3 hours now and can't find anything.