Actual that's "dual injection" you are referring to...
I had my intake valves cleaned at a little over 50k and BMW's carbon buildup is nowhere near as bad as the carbon build up in VAG direct injection engines, the RS4 in particular....My valves had very little build up and I wasn't experiencing any issues at the time.
I'm experiencing issues have been for the past 3 months or so. The car has a hesitation at highway speeds that didn't go away even after the plugs were changed. All of the BMW techs and indy guys knew exactly what the problem was. BMW won't cover it under warranty though.
I expect the valves to look like shyt.