Just to add to Doc's thread.
When i rebuilt my MPS3 turbo i did a oil volume check at idle and found it to be supplying far too much oil to the turbo. I fitted a brass restrictor "pill" in to the stock banjo bolt and then proceeded to enlarge the hole (up from 1mm) until it supplied the correct amount of oil that i was told for the turbo. If my memory serves me correct the hole ended up being 1.45mm.... the car has and stil is running like a charm 2 years later