I think you need a 4E0 G or H suffix..
http://www.dognmonkey.com/audi/a8-d3...-retrofit.html
of a 4L0 B (Q7).
I fitted 4L0 B and can confirm it works....
Address 19: CAN Gateway Labels: 4L0-910-468.clb
Part No SW: 4L0 910 468 A HW: 4L0 907 468 B
Component: J533__Gateway H06 0060
Revision: 00H06000 Serial number: 1100B079038194
Coding: F5F9FF7F507E0E00
Shop #: WSC 02313 785 00200
VCID: 2D5A8011B447A856E5-8078