Truck Repair: Cummins N-14 Plus Low Power, dodge cummins, cummins engines

Question
This engine will (eventually) get a full load up to 78 mph. But it won't climb or accelerate at all. It is actually a bit dangerous in a merging situation on highway. It simply falls flat on it's face. It has a new wiring harness, new TPS (APPS?) and numerous fuel filters. It has been checked by a private mechanic several times. (Owner is too cheap to take it to Cummins dealership)

Owner is ready to give up on it and wants to sell it. Truck is in remarkable shape( because it is so slow!) and is a pleasure to drive ON THE OPEN HIGHWAY once it reaches 60 mph on flat ground. It has no boost gauge but the post turbo pyrometer will reach 900 degrees F max. I drive this lemon and was thinking about buying it, if I can fix the acceleration. I don't want a hot rod, I just want it to drive like a regular Cummins engine in a used truck. I'm funny about merging onto a highway at about 50 mph. I merge at 30 mph if it's downhill and I'm lucky.

 I think it's a fuel issue, and here's why. When it is warm and I shut it off, it will crank for 5 or 6 seconds before it will fire. If I push the skinny pedal just a bit, it will fire right off.
It idles fine, but it will only rev to 2100 rpm. (Governor?) Is the fuel line too small or what? I swear my '01 Dodge Cummins will make this thing cry like a girl.  

Answer
Cummins engines have been known to have problems with plug at the rear of the engine computer --- the pins in the computer will break off and/or the plug will rot away --- as for the 2100 rpm -- that sounds like the proper governed limit.  


Also if possible have fuel pressure checked at the engine.