Take it to auto zone and they will read the codes for free,the light does'nt have to be on for it to have pending codes.this is a good place to start.it sounds like you have an intermitant problem,coming and going.maybe you can find it before it goes out for good.however it may be something very simple.with these trucks it usually is.you say the fuel pressure is fine,did you try unpluging the vaccum hose to the pressure regulator with the truck running and see if the pressure came up by about 10psi ? and is there gas being sucked into the vaccum hose to the regulator?