No cars are pre-wired for nav. You are probably looking at the connector plug for the telephone control unit.

The navigation wiring is radically different from non-nav wiring. The major differences are that the radio is located in the trunk (instead of the dash), and you a pair of plugs that carries the video signals from the trunk to the dash for the display. However, it is a pretty well-understand retrofit project, once you get the navigation harness from the dealer or used source.

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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