Does your truck have a turbo? Does it at least have a free flowing 3" or bigger exhaust and the soup bowl cut out? Turning up the pump on a N/A gains a bit of performance but probably more black smoke than anything else. I don't know if its right to say that turning up the fuel increases fuel deleivery pressure...it may be. I prefer to think that you are shifting the fuel delivery curve such that more fuel is injected at any throttle position. The limiting factor is of course do you have enough air to burn the extra fuel? The first question is do you have much black smoke now? if not you probably have room to play...though everyone's advice about a pyrometer is good advice...get one, mount it close to the manifold, watch it. Turning up the fuel requires you to take off the little triangular cover on the passenger side of the injection pump and bring the engine to TDC fuel shutoff solenoid disconnected of course and then when you can see the allen screw, use a 5/32 allen wrench of good quality and turn the screw clockwise. It'll have a lot of resistance and not move very far, about 3 flats or 1/2 of a full turn maxes the pump out from what I hear. The whole time my truck was N/A I left the fuel to the calibration the pump builder set it at. When I put on the turbo and a rebuilt pump, I turned up the fuel before I put it in. I bottomed out the screw then backed off about a flat and a half. If I did it right(questionable) then I'm somewhere between stock N/A calibration and maxed out. I can't make EGTs higher than 650 even at 80mph with an empty truck...max turbo boost is only around 4-5psi with an old ATS no gated unit. Zigg has a more detailed, more expertly written article on turning up the pump.... you should read it and then decide if you want to or not. If you have a turbo, you need to do it, if you're N/A its a tough call.
