Check the voltage at the fuel pump - should be 12v or nearly so. If you don't know when the fuel filter was replaced, replace it now.

There's no easy way I know to check the fuel pump..... our trucks really need a test port on the fuel rail.

On the off chance you have a sticking/fouled injector, you can try running some injector cleaner through the next tank of gas and see if it improves things. I'd recommend BG 44K if you can find it.... if not, use Techron.

If your problem is indeed fuel related, I think it's the hardest thing to diagnose and prove on our trucks.

Oh, check all of the vacuum lines, but particularly the one that plugs into the fuel pressure regulator (on the rear of the fuel rail - passenger side).

Frank