I have a 2003 X 6.0 and about twice a week just cruising along I come to a hill and when I accelerate it starts to billow black smoke and starts jurking while I"m hearing a thaw thaw thaw noise.
Normally when I stomp it to the floor it will come out of it .
The one time the dealer had it they replaced the turbo accuator but it did"nt help.It almost feels like a bad throttle position sensor.
Any ideas?

109000 miles

 

EGR is plugged up and stuck open. You are running too rich as a result.

Once the EGR is cleaned up / closed--accidentally disconnect it!

 

Yup, EGR. Long answer here, amongst other places.