I would try to trace the wires currently connected to the Aux pins. Maybe the previous owner already connected the Aux input.

Alternatively, temporarily remove the pins taking up the Aux positions and connect your new aux kit to the plug. Then, see if your aux kit works. If it does, then you might just keep it as-is.

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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