I think the V8s are notorious for valve stem seals so I'm guessing by "white" smoke you mean not black. Clearing adaptations is a good thing but NOT with the engine running. AFAIK, very unlikely that the problem is the DME/ECM so I wouldn't start with that.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)