Manifold/header/muffler/tail Pipe problems of the 2010 BMW 335

Excessive soot and carbon build up in the intake manifold and intake valves of the 335d which is a diesel car. This causes rough idling, misfires, and loss of engine power. While merging onto a highway, the engine malfunctioned due to this problem and immediately lost power almost causing a collision. The vehicle has had this problem for more than 20k miles and continous trips to the dealer to diagnose. Finally, the dealer agreed it was carbon build up but that it is not covered. The repairs for this should be covered by BMW as it is emissions related and can cause significant engine problems. This has not been an issue on other diesel cars by other manufacturers.