Noticed similar thing when I got my A3... Took back to Audi to get everything checked out and they did a full tracking check, column adjuctments etc... and found it to be spot on. They suggested it was to do with the car being VERY sensitive to the camber in the road, and suggested I try driving (When safe to do so) on the other side of the road and the car will pull with the camber to the right. Tried this (On a quiet stretch) and found it then pulled to the right. So it just seems that they are very sensitive to camber.
Just had a my steering column replaced too and found that even though all the steering geometry has been re-aligned as part of the fitting, this has made no difference so deffo camber sensitive.
One thing I did notice is if I had a high tyre pressure, around 33 on the front, the effect would be more pronounced, so try adjusting tyre pressures to suit.