Smgkw, are you talking about the rough downshifting on DECELERATION (when you brake or ease up on the gas)? Some of us have had problems with that and there have been a few threads on the subject. "Kickdown" refers to downshifting with maximum ACCELERATION (downshifting several gears when you floor it).
If you're talking about rough downshifting during DECELERATION, I'd be most interested in knowing more about that "modification." What exactly did your dealership's techie tell you? What parts are replaced? Can you get more info, like an MB repair code number that I could give to my dealer?