want to send XM receiver's line level to 95 E300 factory head's CD input

[Guest (MBNZ)]

I currently have a Pioneer 903 XM receiver installed in my '95 E300. It's sending its FM signal to the factory head. I'm not happy with the sound quality, though and I want to keep my factory head. I'm told there may be a way to send the XM's line level signal from its IP-bus connector to the CD input on the factory head through the factory CD changer connector in the trunk. My car is prewired for a CD changer, but none is installed. Fooling the factory head into thinking there is actually a CD player installed is the problem. Peripheral-AAMP has CD changer interface products for most cars, but I can't seem to find one for my model Mercedes. (BTY, my car was manufactured 7/94) Does someone know the pin-out specs(with voltage states) of the Mercedes plug in the trunk for the CD changer?