Repair wires 000-979-009 fit in the quadlock connector, the positions for the AUX IN are marked on the label on top of the radio. Recoding is required to enable the AUX IN, after doing so you can connect almost any audio device.

http://www.navplus.us/forums/showthread.php?t=3274
http://wiki.ross-tech.com/index.php/Audi_Radio_Generation_II_Plus

_{2004 A4 3.0Q Tip Avant Ultra Sport, Moro, Premium, Cold Weather, Bose, XM, OEM Bluetooth, Color DIS}
^{RNS-E, Audi iPod with XM}