i have been told that the cure for this problem will be availiable in October of this year from Audi. They say the bushings are not right for car set up thus cause vibration.

Saw this on another forum. Hope it helps:

Hi guys. I've been reading this thread and site for some time now,
decided to register to report my story on steering wheel vibrations.

I have a few weeks old 2009 A5 with normal servotronic, 17" stock wheels with
Michelin Primacy tires and the sport chassis, not the lower S-line chassis, but
the regular optional sport chassis.

Up to 2500 kilometers I had no vibrations problems, but after hitting a curb and
having one front wheel and tire which was externally damaged a bit replaced and
wheels realigned, a shimmy developed in the steering wheel at motorway speeds
starting around 100 km/h. It was very visible taking hands off the steering
wheel and most visible on very flat, new pavement. The shimmy wasn't caused by
the curb hit, the problem started after the wheel and tire were replaced.

The other wheels had lost maybe 1 mm of their surface due to wear, so the new
wheel was a bit different but not much. I toyed with different tire pressures,
but the shimmy didn't change much. The shimmy happened both when the wheels were
cold and when they were heated after driving.

Back to the shop, all wheels removed and balanced, only to be found to be pretty
much perfectly balanced. Wheels put back on, test drive - no more shimmy. The
wheels may have been improperly centered, so do check that your wheels are
centered and tightened properly so that they won't move out of center while
tightening. Sometimes just putting the car up on blocks, removing and
retightening all wheels might help.

Not the end of the story though. A few cold mornings later the shimmy
resurfaced. Not as bad as before, but still felt and visible. Test drive in the
evening, no shimmy. I was puzzled, the shimmy was now coming and going. One
morning when the shimmy was back, I decided to re-drive my morning route right
after getting to my destination. And you know what, no more shimmy on the same
piece of motorway I drove 15 minutes earlier. It had to be cold tires, temporary
flat-spotting maybe, or more likely just the other front wheel, the new one,
taking more time to behave like the older one.

Back to the shop, front wheels to back, back wheels to front. No shimmy yet, nor
any other unwanted vibrations. I do see A5 being more sensitive to road
imperfections than some cars I've driven, though.

So some ideas to check:

Make sure your wheels are centered and tightened properly.
Make sure your wheels are balanced.
Check tire pressures so that they are manufacturer recommended.
Check if the problem occurs only with cold wheels.
Move front wheels to back or the ones with lower road force to front.

Talking with the maintenance shop again after reading the Audi America technical
bulletin posted here, they too are now starting to take note of the road force
values and said they have had problems with cars with too high road force values
tires. The bulletin recommends putting lowest road force tires to the front.

Clearly some cars are more vulnerable to tire differences, A5 seems to be one of
those.