Screaching from the turbo 300tdt

[Gordo]

I did a search and could not find anything quite like this.

The Problem:
My 1980 300td now with a engine from an 1983 300d (long story) has developed a sound that seems to be coming from the turbo. It is a terrible screeching noise. It happens when the engine is warm and under load at aprox. 2500RPM. The pitch varies with load. It sometimes starts as an intermittent chirp and then becomes constant. It is hard to tell if there is any loss of power.

What I Have Done So Far:
Yesterday I removed the turbo and replaced it with one I had on a parts motor that never had turbo problems. PITA. The car seemed to run fine with the "new" turbo until I drove home to the mountains. The sound had a slightly different tone to it, but is back at least as bad as before.

What could this be? I think it must have something to do with the turbo since it changes with load and seems to be coming right from that area... But, how could both turbos be doing the same thing? Could the turbo be starved for oil? Any help would be great. Thanks.