"Bushings,Idler Arms, Sway Bar, Tie Rods, Ball Joints, struts, springs, all check out, no need to replace."
I think you need to re-check this area.
I had a shimmy in my '95 E320. Changed the steering damper, checked wheel balance, tried other wheels/tires finally swapped in a set of new struts/ shock absorbers. That fixed it.