That is an old article on a motor that is not used anymore. That design of valve overlap can no longer be used due to tightend emissions regs There newer motors have carbon issues. The DI motors that don't are the ones that also have port injection. Also, BMW knows about it and has specific tools to clean it. You just have a poor dealer. All good BMW techs know about it especially on the older V12 7 series cars from back in the day. If you had an audi, you would be doing carbon cleaning once a year!
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