I changed my vaccum pump on my truck about 3 -4 weeks ago. I heard something loose under the hood, end up being the centre cap on the vaccum pump was rattling around, I could of just pulled it off at that point. I ended up turning it tight with pliers but the cap wasn't sealed fully against the housing. I took a vaccum gauge reading at the turbo whichs is 12-17 psi at idle. Now when I gas it, I bearly hear the turbo whine, and the truck doesn't have that pull as it use to, black smoke at times, I also hear my wastegate solenoid could be at fault.

Start in this FAQ link http://dieselplace.com/forum/showthread.php?t=16888 I just peeked at it quick 4 pages ought to be something in there, if not I'll use this thread to kick off a trouble shooting thread, let me know Crowne if more is needed than the info in the sticky I linked you to here.

Thanks Doc on the link, The center cap ended up being just a front cover on the pump, no rubber seal of some kind around the cap. I just took a vacuum reading off the red line by the wastegate solenoid which run back to the vacuum pump, reads 25 psi, sounds like the pump is fine. I'll be changing the wastegate solenoid tomorrow after work.