Engine/Transmission (1994 - 1998) Blue and White smoke, no power. What is it?

[Blacksdieselhp]

Truck will smoke white and blue when accelerating. It has a 10 plate in it. Runs great and then all of the sudden it will fall on its face and start blowng smoke. Also when you push the clutch in after it does this, It will run a little rough then smooth out, like its running out of fuel then picking it back up. My guess is the lift pump because of that. Also when just sitting, you can rev it up and get a greyish smoke. Kinda like one thats out of time, but this one runs god sometimes and then it just happens, so I don't think its timing. but I thought I'd ask you guys before I started on it. Thought someone might have had the same problem. By the way, its a 97' 5 speed.

 

[CSimpson]

change fuel filter, check pressure, I had to replace my overflow valve... . I had low pressure, and was running rough, overflow valve is a lot less then lift pump, and it doesn't hurt to try those options first.....