Truck Repair: bad performance, air filter oil, vp44

Question
Sometimes on flat land I can go no faster than seventy. I loose power going uphill, but when I put the truck in neutral. I let it idle for a few seconds, It regains power for a few miles. When I am going downhill it lets out blue smoke. however it does not burn oil. I changed the air filter, oil filter, fuel filter, the fuel transfer pump, and the throttle postion sensor. Yet I still have problems and I can't afford a VP44.

Answer
I have seen a few VP44s go bad & not log faults.They have changed them somewhat to cure these problems & make them more reliable.Sounds like you have done most of the first things to change.A road trip with a laptop will do wonders for finding a bad sensor or just to see what the engine ECM is doing to the engine.