If you have a laptop, buy VAGCOM VCDS HEX CAN for £100 ish.
I did this to find faults, but turned up other problems.
I have looked at two A6s so far and both were found to be clocked when I ran a scan.
It seems they clock them every year before the MOTs so that the mileages on only MOTs look OK.
e.g. The mileage was 11000Km lower this month than in march, similar story since 2009.
Address 0E: Media Player 1 Labels: 4E0-910-111.lbl
Part No SW: 4E0 910 111 C HW: 4E0 035 111
Component: CD-Changer H44 0340
Revision: 00000000 Serial number: AUZ5ZBD4025313
Shop #: WSC 00000 000 00000
VCID: 193244C1AE83
2 Faults Found:
02261 - Data Medium
014 - Defective - Intermittent
Freeze Frame:
Fault Status: 00101110
Fault Priority: 7
Fault Frequency: 2
Reset counter: 191
Mileage: 222028 km
Time Indication: 0
Date: 2011.10.13
Time: 20:03:46
Freeze Frame:
Text: 0000840E
00532 - Supply Voltage B+
002 - Lower Limit Exceeded - Intermittent
Freeze Frame:
Fault Status: 00100010
Fault Priority: 7
Fault Frequency: 7
Reset counter: 198
Mileage: 233369 km
Time Indication: 0
Date: 2011.03.04
Time: 07:32:27