If you are getting black smoke under accelaration, or after letting off and stepping back on the gas, I would bet its just too much fuel being dumped into the cylinder before the turbo has time to spin back up. Seal rings in the Turbo could be worn out. Its what happend to my 97 cummins. So far my 97 ford only smokes when I start it cold, and when i put it to the wood but i have it set up to do that.
Tyler, November 2008