Hi I have a similar problem but not from the front. A juddering from underneath/rear the car when going from a standstill with full lock in and accelerating briskly. Mine only happens when warmed up.
There is a TPi or TSB whatever it's called for Quattro Ultra.. So far they've done a software update and a clutch adaptation (twice) but it isn't fixed. It goes in next week for a clutch pack replacement on the rear transmission.
My car is fortunately still under Manufacturer's warranty.