I ran into issues with that CD Changer when used with Sirius. The sound was very distorted when I hooked via the Sirius Satellite receiver, although was fine when it was hooked directly to the CD Changer car wiring loom.

I learnt that the changer was pretty old in terms of when it was released. Apparently BMW made some changes to the audio pre-out on post 404 changers .... whether this was for Sirius receiver compatibility, I'm not sure. Anway, I installed a later CD Changer part number, and it worked fine with Sirius ... so they did something to the changer design I suspect.

This may help, as I notice you have Sirius from your signature.