I went through the surging problem from hell with my '96 E300D. It was one of the first of these to be shipped, and I suppose they hadn't figured out the problem yet. My car was their guinea pig. They ended up replacing ALL the valves for the resonance system. The problem went away. I'm sure they can home in on it much better now. With MB Doc's experience with this problem now, he could have probably replaced one part the first time and fixed it. Nothing like intelligence and experience with a particular system to make a good troubleshooter.
Have a great day,