Is it a possibility the carriers are different if running a 320mm disc?
They change all the time. The current S3 ones have little wings at the top and bottom. Is their no part no. anywhere?
Mine are identical to Carl's pics.Hopefully Dave B will be along shortly Have you searched for any info on revisions to the brakes (other than the 'wings')? They deffo look like a 345mm setup, but the differences are clear.
Some audis do run with 321mm discs, so could they be from a top end A4/A6???
Look like MK2 TT V6 calipers to me. Only 345mm calipers that didn't come painted.