I have a 2010 cL550 with the m273 engine(with 100k miles) which is the same platform as your s550 and without a doubt I’ve been noticing the same exact thing, problem is I’m not sure if it’s always been like that or it’s something new..I’ve heard it could have something to do with spark plugs and ignition coils, as well as an aging fuel pump..I plan on replacing all the plugs and coils as soon as possible as this should have been done by now anyway, I’ll report back on that note. How many miles on your car? What year?..anyone else chime in on this as I’ve been meaning to ask the same question.

yes, also heard it could be a vacuum leak or clogged air filter(neither of which are the culprit on my car) I forgot to mention it’s also more pronounced if I’m coasting downhill. Same with you?

Yea i doubt its my air filters either i just changed them out a week before the spark plugs. It would be nice if other w221 owners could test it on there vehicle and chime in. In my head i want to say if your going fast and hit the brakes it makes the car downshift to a lower gear in turn raising the rpms for a moment then regulate after but this is a benz you would think it would throw it in a low enough gear to wear it wouldnt do that but hopefully more ppl comment and we can gather data