Check out this post to solve the whine. It may be that the ground pin on the Sirius-to-CD adapter is incorrect.

http://www.bimmerboard.com/forums/posts/110947/

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2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input