Sounds like you're leaking boost and the injection is injecting too much
fuel for the air that's actually making it into the engine. Check all the
rubber hoses between the turbo and the engine, particularly the couplers
between the metal pipes and the intercooler. Pull them off and poke from
inside with your fingers, I've seen them rip a flap that only opens up under
boost.

yep...i agree w/james...porb a broken or cracked turbo hose...check the
big ones 1st...have a friend sit in the car and "punch it" and let
off...see if you see a hose acting up....

ucsb...nice school....great location...how are things in sb county? i
spent 50% of my youth in that area...what are you studying?

I doubt it is a torn turbo hose - those give symptoms of being normal until
a moderate amount of throttle is called for, then the turbo starts spinning
(even when the throttle keeps the boost from getting to the manifold) and
the mixture goes *way* rich (as the others have noted) and the power drops
like a stone... but it doesn't start running right until the engine has
idled down and the turbo has spun down. It produces an odd "fold-back"
throttle feel - just backing off a bit doesn't help; you have to take your
foot off completely for a few seconds to go again. Going up hills is very
difficult.

Our '85 765T did the black smoke and poor power under boost for a couple
years before I stumbled on the problem. The cylinder head temp sensor under
the manifold branch between the #3 and #4 cylinder - not visible without a
mirror - was making intermittent contact. (It started a couple months after
I changed the engine harness, but I didn't make the connection between the
two events.) Try reseating the connector. It has a press-to-release wire
spring latch and can be reached by sticking your arm way back past the
throttle body. It isn't terribly hard to work with once you get your fingers
on it. Ours occasionally has to be reseated still, but it has been over a
year since the last time.

Mike