I am not a turbo diesel expert either but when we were getting ready to
purchase our '86 Turbo diesel Jetta I spoke to a friend of mine who was a VW
tech for many years.  He said that high oil consumption on a turbo diesel VW
usually meant that the turbo was going bad (seals or bearings internally I
forget which).
You should be able to check the cylinders for leak down (to see if the rings
and valves are good).  If they are and there is no large oil slick under the
motor, then I would say that the turbo has to be the culprit.

Hope this helps,
Ken Wilford
http://www.vanagain.com
John 3:16
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