I have identified my lift pump as the probable source of low power under load on one of my 1994 6.5TD flatbeds.

I have power to the pump with the truck running, unhooked the lead and had same performance WITHOUT the lift pump! I am somewhat amazed that the truck will still pull a trailer, 7,000 bobcat, etc. just on the injector pump alone. Probably only due to 4.10 gearing...

Question: GM charges $199 for their pump, NAPA charges $99. Anyone used the NAPA replacement? What about inline performance aftermarket pumps?
Can you gain any added performance by slightly over-pressuring the lift pump?