There is a couple of threads on this subject. One of the eBay sellers is recommended. If you buy your kit from him you can send your Turbine and Compressore wheels to him and he will clean and balance them at a resonable price.
On some Turbos the all of the rotating parts are balanced as an assembly.
On others or by request you can have them balanced individually.

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84 300D, 82 Volvo 244Gl Diesel