I have seen a faulty fuel damper hose cause this on the older D's... I have a '96 and it runs quiet and smooth. I would get this cured!
Also, be sure that the tires are a good brand (Michelin mxv4) and have the same amount of wear all of the way around.

__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS