yes, this is happening in all of our direct injection motors as well!
The 760 V12 motor gets it pretty bad and that is A LOT of valves to clean out every 35-50k miles. Factory warranty will pay for it but a CPO warranty will not!
I tell you what is really funny, when I talk to 'BMW technical services' about it each time a customer comes in for a misfire complaint which turns out to be valve deposit case, they say, " tell the customer to use good gas"
Then i say, WHY??? IT IS DIRECT INJECTION!!! YOU FOOLS!
This problem and the secondary air carbon deposit problem are all reasons why you should just flog the hell out of the engine every single time... If you drive them nice, they will kill themselves.