The 540d has swirl flaps on the intake manifold to regulate air intake so it adjusts how much air the intake manifold feeds the engine. There's an actuator motor that connects to the swirl flap shaft that connects via a plastic linkage. When the linkage breaks, the flaps are no longer controlled by the actuator and stays in its semi closed state. The result is when you give it full throttle, it spews out plumes of black smoke that is thick and the equivalent to rolling coal on a deleted diesel truck. The car still runs, but this poses a danger to those behind you and not very environmentally friendly to spew out soot. BMW's solution is a $6,000 repair bill, because the entire intake manifold has to be replaced for that linkage. This will be a guaranteed fail again - considering I had a check engine light for swirl flap issues starting around 40K miles.
NHTSA ODI 11602418