Owners of a 2011 BMW 328i xDrive vehicle (equipped with the N54 engine) may complain of a slight rattle noise from the engine compartment after shutting off the engine. The noise is similar to that of a mechanical typewriter. In addition, the owner may complain about a slight reduction of power, similar to an increased turbo lag.
The vacuum supply to the waste gates may be restricted or blocked. The vacuum supply hoses that connect the pressure converter or vacuum solenoid (EPDM) can kink if they are bent too sharply or not installed in the hose retaining clip properly. Consider re-routing the vacuum supply hose to prevent kinking.