Don't have a compression tester for a diesel, I'll pick one up this weekend but it seems to me that its to intermittent to be compression related.

I checked the fuel lines, found a rusted line to the tank, replaced the line all the way back to the tank. Pulled the filter screen from the tank, it was clean.

Let it warm up, took it out for a drive, it drove great for a few minutes. When it starts to run crappy there is gray smoke, floor it and I get a little black smoke until the turbo spools up, then its pretty clean. Turbo is pulling about 9psi (thought these were supposed to be 10-12?) When it runs crappy if you pup it into neutral and rev it the fist few times you rev it up it clacks like the injection timing is off. Two/3 revs and it sounds fine. Pop it back into gear and it usually will drive pretty good for a few secs or a minute or two.

Do you really think this could be compression related? It seems to inconsistent for that. About the only thing I can think of that I didn't check was injector nozzles. Guess I'll pull those out today.