Lots of black smoke, not the best power

excessive fuel and if turbo operation , failing turbo
check for excessive fuel pressure , leaking injector seals
turbo not operating

Best I can tell this is a diesel truck? I know diesel, but
depending on age could be injectors, possibly Diesel injection pump hopefully not. The fuel is black? Someone is putting old engine lubricating oil in the fuel tank. It will increase the problem of black smoke. It may also have a bad smell because of the engine oil. If the turbo is not spinning properly (high pitched whine) the bearings may be bad and it's not getting enough air into the engine. This would also explain the smoke problem. Take it to a Diesel specialist!

Diesel engines smoke when under a heavy load. Unlike a gas engines, a diesel engine uses fuel that is more like an oil.Smoking is a good indication the fuel is not completly burning because of loaded engine spee. White smoke indicates the fuel is not ignitingefficiently. Truck, boats, tanks abd anything else using diesel fuel will smoke when it gets more fuel than it can use.. Easing up on the throttle will lessen the smoke but not eliminate.. Of coarse if the demand is lessened by applying less loadyhe fuel consumption drops.Not to worry as long as the smoke doesn't attract the EPA.

run fault codes and look for EGR valve and pcv valve faults. Black smoke is unburnt diesel so it may be the injectors need attention. If it is a turbo then check the oil lines to the turbo and check turbo operation as it may not be producing air pressure for the engine.

replace the boost sensor its about $60 that will clear the PO236 codes (i beleive that was the code)
Duralast part # is su129 and has a lifetime warranty. located under the "turbo power" engine cover if you havent removed that yet take it off and leave it off reduces heat
sounds like your vacuum pump is bad remove it, buy a 99.5" serpentine belt and do a mechanical wastegate. adjust the spring to the boost you want. good luck

You need to have the electronic engine control system scanned for fault codes, that is the very 1st step in diagnosis of this problem.

check fuel filtres and clean lines

black smoke is not enough air or excessive fuel
if turbo , the turbo is not working and boosting, injector failure
incorrect fuel in system ( petrol instead of diesel)
water in fuel will damage injector tips

The turbo will not cause black smoke. White smoke, yes, if its passing oil into the engine, but not black.
First check that the air intake and filter is not blocked, check that the air hoses from the turbo and intercooler are not collapsing when given throttle.if thats ok, then get the injectors tested, if they are ok then you need to get the injection pump serviced. Black smoke is a result of overfuelling, either by the poor dispersal of fuel from the injectors or the pump, or blockage of air into the engine on the intake system.
Hope that helps

Sounds like maybe one of your injectors is know working, I would start with that. Please let me know if this helps. Any other questions on this please ask.

Cheers