Have you checked the Sirius/CDC slave cable as described in this thread?
Originally Posted by Reach
So, you have OEM Sirius and a USA SPEC PA-12 iPod adapter on the OEM Sirius slave port and zero undesirable noise on the iPod connection?
That bold part is the bit that has dogged me for some time. I have used an iSimple in the past and a Intravee now. Looking for an iPod interface which will give clean audio after the OEM Sirius & let me use the ipod click wheel or screen of my iPod Touch, which the Intravee solution will not.
2003 M5, Carbon Black, Nav, Intravee II with Ipod + MP3 CD Changer + DAB + MD Changer, TV, Bluetooth Phone, the works.
2013 M6 Gran Coupe, Sakhir Orange, Competition Pack, Ceramic Brakes and lots of other options