whats the cheapest place to get the RS4 turbos(Complete Upgrade Kit), on the 2.7 engine, since iam only a medical student money is short by me, and also are there any other turbos that will work with the 2.7 engine instead of the RS4 turbos?

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2000 A6 2.7T 6M (Stage 2)
1995 Audi 90sport