A few more words on this little beauty....
Not a cheap addition to the car,but by comparison with something like say the Haldex controller,which costs about the same sort of money,the value in terms of grip and handling is way better.
Yes,the 2 compliment each other,and I suppose ideally you'd have both(I already had the controller and waited until Quaife produced a diff for the 4WD gearbox),but this thing really does do the job.
On a wet road,like today,traction is better,and more secure under acceleration,and the car doesn't feel like it's fighting you every inch of the way.
It's therefore smoother and easier to drive,less of a handful,and more predictable,but as I said earlier,it doesn't seem as snappy as previous Quaife ATB diffs I've used a while ago.
It does show up how bad a decision it was for Audi to stick a simple open diff in the car.