I may be throwing the hail mary pass, but ive had it once, where the fuel pump /fuel filter, wasnt able to supply enough fuel and thereby caused a misfire, (BMW also adds fuel cut off if it detects too lean (no fuel??) and shuts off the injector(s) in question.
I was able to solve this issue by changing out the fuel filter and reconfirming fuel pressure from the pump. (but not untill most of the ignition system was changed.!)
my big clue was that even with NEW coils and NEW plugs i still had a RANDOM misfire with fuel cut off. meaning there was still not enough fuel randomly dribbling out of an injector somewhere to produce adequet spark!
just my $.02 worth

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2003 X5 3.0i (02/2003) sport package, Sapphire black metallic / Black Dakota Sport seats. compass mirror retrofit, trailer hitch retrofit, Prodigy P2 trailer brake controller installed, PDC retrofit, Lumbar support retrofit. heated rear seats retrofitted. Running boards retrofitted and subwoofer install in progress. 4.8is Brakes installed front and back. Bluetooth TCU installed, Rear Fog lights installed. Retrofitted reclining rear seat backs.