I have a 2003 chevy 2500 with a 6.0. It just started cutting out and now the A/C is not working. We have replaced spark plugs, wires, MAF, air filter, and its still missing. It starts right up and doesn't die, but idles roughly. Idk if the a/c has anything to do with the rest of it, but it has me stumped. I dont want to go and replace the expensive and hard to get to fuel pump until i can make sure its not something else. Any suggestions?