I have the same/similar issue. The car vibrates starting about 35mph and mostly gone by the time you hit 45. It is most noticeable under light acceleration as you move through those speeds. At heavy acceleration you only spend like .5 seconds at those speeds and probably just don't have time to feel it. If you keep a steady speed it pretty much isn't there as well as decelerating. It is pretty much only there when the car is "cold". After 15 or 20 minutes of driving, I can't feel it. It is in the yoke most obviously, but also the accelerator pedal and ever so slightly you can feel it in the seat. It is a vibration that I liken to making a "vvvvvvvv" sound. Perhaps 30 hz range. I have talked to the service center about it and they say they can't reproduce it. I am quite certain they just don't want to, it isn't really pretty easily felt. I believe it has something to do with the motors, even though it feels like bearings. If it were bearings/half axel/etc, it would not go away when the car warms up. The fact that it is only felt with acceleration and not deceleration or steady speed makes me believe it is not a mechanical component but rather the motor and how it is developing the magnetic field and moving the rotor through that field.
