My 2002 ML55 (10k miles) is giving me fits. I've tried Shell, Amoco, Phillips 66, and other premium gases. ALL cause a very foul (sulpher?) odor to come ito the passenger compartment whenever I have the rear vents open. The dealer says there is nothing wrong - no "codes" found on their computer. Also, if I back up out of a parking spot and throw it into 1st gear, the tranny doesn't engage right away. Again, dealer says no problem because no "codes" found. Help??