Have them check the High Pressure Fuel Pump, Fuel Injectors, Fuel Rail and Turbos (all common issues with the 535).
[B]2008 550 - Carbon Black/Black - M-sport, Cold Weather, Premium, NAV, Comfort Access, Logic 7 (LOADED, every option except night vision)
Previous 3 cars (the 550 is my 38th car):
2005 530i - Prem, Sport, NAV
2006 Jeep SRT-8
2003 Infiniti G35 coupe