1994 c3500hd black smoke ??

[Americanhooking]

I have a 1994 Chevy C3500HD 6.5 turbo 5 speed roll back tow truck with about 130,000 miles on it.
My question is why would it all the sudden start to blow some black smoke while shifting especially with a load on it
will also do it sitting still if i stomp on fuel pedal. Seems to have also lost a little bit of power taking off also up a incline. You can hear the turbo spool up while shifting only smokes while shifting and when you stomp pedal while sitting still. Drives fine on the highway and while cruising down the road . Has a brand new air cleaner
I have checked the wastegate actuator linkage while running and you can not move it at all. also checked the vacuum at waste gate and at pump. I put vacuum gauge on orange line at waste gate and got 25 in-HG i also checked line coming from waste gate actuator and got 15 in-HG.
Replaced the wastegate solenoid just in case and checked vacuum and got same readings.
I have also changed the turbo boost sensor. The exhaust is straight piped
Any help would be great im a small business owner with a new business i cant afford to keep throwing parts at this if it not going to fix the problem

Will it harm the engine to keep driving it like this???

[More Power]

Replaced the wastegate solenoid just in case and checked vacuum and got same readings.

I suspect your original wastegate solenoid was bad. Then the in/out vacuum lines were inadvertently swapped during installation of the new solenoid (that happens a lot - unless the lines were labeled before removal). The vacuum wastegate system won't operate correctly with that situation... Another possibility is that one of the fragile plastic vacuum lines was cracked during the repair... causing a loss in vacuum.

Jim