I added some pics above of what they're supposed to look like. The only thing I can think the second filament in the tail light is used for is adaptive brake lights, which didn't exist prior to MY 2003, and even then the lights in the tailgate are the ones supposed to light up.

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Gone, but not forgotten:
2003 X5 3.0i - 135k - the most expensive club in the world.
Premium, Cold Climate, Rear Climate

Service History

Mods and Retrofits: Satellite radio, MediaBridge, DEPO HIDs + LED AEs, M-B W164 rear-light mod, clear corners, BSW x108 Subwoofer System, illuminated door handles, titanium grill, compass/auto-dim mirror

Traded 9/1/16 -- 5UXFA53533LV80809 -- If you know his whereabouts, please contact me.