For what it's worth, I spoke to a friend of mine who owns a BMW repair shopping San Francisco. He said this problem only affects about 10% of the N62 engines. So don't panic quit yet. But it is something to keep an eye on.
Thanks for that - I love getting "rare" expensive problems. The flipside is that my (later model) supercharger hasn't detonated - and remains oil leak free!
The Alpina has now been moved to the BMW dealer who will rebuild the engine - a mere 9k (assuming no further Alpina part specific damage) to fix!
Sod the little girls, thank heavens for all inclusive warranties.
