Do oil change every 10,000 km. Dont follow the bmw recommended range.
My friend's N54 was doing 380 km/tank (He used to follow the bmw recommended range, and would only do it when car "needs" it). I told him to do every 10000 km and after his oil change he gets 500km/tank. Don't know if it is related but he actually got better mileage after.
Performance Intake and Exhaust, Apex arc-8, KW v1, Vorshlag camber, ER brake lines, Lux V4, AA tune