Just bought a 2009 Brabus and days after passing emissions the check engine light came on. Dealership said it was because air filter cover was loose and filter was dirty (CarMax and VIN showed MB only did 10K checkup, it has 53K miles now) causing a lean mixture. Agreed I could change my own oil and filter, air filter (K&N) and cabin AC filter and everything else could wait until major 60K checkup. They re-attached the air cleaner cover, adjusted the fuel mixture and cleared the check engine light error code. That was Monday. THURSDAY (before I could get the parts) the check engine light came on again and a car parts store diagnosed that the error code now said the engine was running rich. Took it back to the dealership who said it was because the filter was dirty. Told them I already knew that and was going to change it myself (they would have charged $100 for an oil change and $100 for another paper air filter!). The dealership did NOT clear the error code or check engine light. When I got home UPS had delivered the parts and when I changed the air filter discovered the dealership had returned the car with the airbox unsealed (none of the three clips were attached) basically UN-repairing what they had repaired on Monday. I have since changed the filter to a K&N (as well as the cabin AC filter and the oil and oil filter, where I discovered someone had EXTREMELY overtorqued the oil plug well beyond the 48 foot pounds ("just beyond hand tight") where it took a breaker bar PLUS an additional bar to break it loose! but I digress.) The check engine light has NOT self corrected itself. Any thoughts or comments? Literally a few days before the light came on the Brabus had PASSED the Maryland Emissions Test.