Ive been there done that. Have the rotors turned or replaced. I have had the same vibration on both of my 420's. Warped rotors will definitely cause problems at high speed often not noticable at low speeds.
Where did you get the new rotors??
Take them back.
I got too many cars!! Insurance eats me alive. Dave
78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k