Hi,
My previous A8,1998 2.8 sport developed a steering noise on full lock,but only for the first initial turns from cold,after a few turns, noise went,but over a period of time the noise got louder and louder and lasted longer.
I used to cringe on reversing from the garage and then turn the wheel because it sounded like a very dry,very worn rattly bearing.
I also changed the pump from A8 parts,hey presto problem gone.I remember at the time of ordering,they did say dont sell many of these,you sure its gone.But after removal there was lots of play in the old pump compared to the replacement one
Hope you get it sorted
.