[:-]Hi can any one tell me if the wire required to run a cd changer fitted in the boot is already installed as a standard item i have a 1999 A4 1.6 auto se

 

Yes, there is always a CD changer cable regardless of an installed Changer. If you look on the drivers side (USA) rear wheel well, the wiring plug is wrapped in a chunk of foam. They can be difficult to find and may require removing the carpet in the trunk.