I also experiance this but depending on which rotors I put on for my AP BBK (I have two sets) vibrations are either more amplified or barely noticable after doing some rotor face cleaning with racing pads. But I would say that ever since I installed my BBK with spacers and then moved to new wheels, the car has never been smooth like it was stock. BIG waste of f*&king money IMHO. Not worth the trouble and more money I've had to through at the problem with alot of the work/testing done by myself to add.
I remember this M3 was smooth as silk at 120mph cruising on the Autobahn, tracks, Nurburgring, even on bumpy crap British highways. I never had any kind of slight or strong wobble in the steering wheel. Now no matter how smooth of a road, new tires, road force balanced, etc. I get over 78mph, its slightly rough, slight vibe in the steering wheel, slight shimmy under braking.
I sold all my OEM wheels and OEM brakes long ago thinking this problem was other issue's that could be fixed. Now I wish I had all my OEM parts to go back. I'd rather have a smooth ride than vibrations that shouldn't be there.
Lesson learned I guess.