Does it creak and rattle at all ride heights? First thought would be TRE's and lower control arm. Have someone turn the steering wheel while on the ground and you listen for the creaking to help pinpoint it.
My A4's lower arm will creak while on the ground, but is quiet and solid when jacked up.
Edit: Just noticed that you have coil overs so only one ride height.
'99 A4 2.8 Tip Quattro(220k miles and still going strong)
'03 Allroad 2.7t Tip (Gen I with OE style front, Bilstein rear)