There have been a number of threads about the phatnoise being installed in A4s
on the AudiWorld forum.
http://forums.audiworld.com/A4/

Try a search of check the faq on the same forum:
http://forums.audiworld.com/a4/msgs/2299748.phtml

wrote:
> Managed to get the glovebox off - no cable - took rear trim off boot
> (what fun!!!) and no cable !!!
>
> The Nav unit has cables going to it but nothing spare!
>
> Am I able to fit a changer/phatnoise? or not.
>
> some pics of the headunit and nav unit here
> http://www.photobox.co.uk/album/2665545
>