FYI. This is common on these cars. My 560 SEL AMG has had this problem since I got it. I cleaned the ICV, replaced check valves in the pump, then went to the stealership. I have a good repor w/the the head tech who said that Mercedes recommend running one bottle (the big one)of Techron through the system, if there is no change do a second bottle. DO NOT put in three! If you do you will have to replace not only the injectors, but also the fuel head. If this doesn't work then the fuel distributer is gummed up, and will have to be replaced as no mere mortal can rebuild them. I got a used one from Silver Star for $400, off a car that came in wrecked, but running. Fixed the problem in about 20 minutes.