I was able to use a system called iPod2Car on my 2001 A6
It connects where the CD changer adapter is in the trunk. If you have a CD
changer, this might not work.
I just ran the cable thru the fold-down seats on the driver side, routed the
cable along the bottom of the seat, and the plugin for the iPod is basically
It is not perfect.. sometimes it loses synch with the track up/down buttons,
but otherwise it has been working well for over 2 years