I am working on a friends truck it is a 97 3500 4x4 dually auto. The truck is stock and has never been turned up. I know it is heavy compared to my first gen but this thing is slow. I took it for a ride and when floored there is little to no smoke at all. Then all of a sudden when it gets to 2500 rpm there is a huge cloud of black smoke that comes out and blacks out the whole street. Now when it does this there does not seem to be any change in power. also it dosent smoke like that every time sometimes you can hold it to the floor and it wont smoke a drop the whole time. The guy that owns the truck says that sometimes when he takes off it feels very powerful and then he will stop and take off again and it doesent have much power at all. I just changed the fuel filter and installed a fuel pressure gauge. There is 22 psi at idle and 38 or so at 2500 so I dont think that fp is causing it. I am not to familiar with how a p pump works I have only messed whith my ve before. I know the ve has a fuel pin and if it was my truck I would be looking to see if the fuel pin was stuck and to make sure there wasnt a boost leak in the line to the afc housing. But I am not sure how this thing works exactly. Sorry for the long post but I wanted to describe the problem as best I could.

 

Could be a number of things, but usually a case of several things all at once simply being worn out on an over 13yr old rig: lift pump weak, overflow valve weak, fuel heater sucking air, timing slipped, and boost leaks.
Alot of times I see the wategate diaphram is blown too, and since 96-98 trucks have that stupid metal crossover boost tube that comes from the AFC tee down to the wastegate, this boost leak causing the afc diaphram not to push forward because of lack of boost pressure getting to it. The backyard way to tell there is disconnect the line at the tee and put a pipe plug in the tee.