A few years ago i bought from an auction a 06 530xit (station wagon) with Dinan exhaust(tips), CF strut bar and a "Dinan 5" badge on the back. I contacted them and after a week i received an answer that this is a scam and they only offer exhaust tips for this model. Later i found it has Dinan throttle body and flash, so everything was real. But the poor guy didnt have a clue.
On-topic, you can probably figure out if the car has a tune by dyno-ing it or by comparing some 1/4 mile trap speeds with another X5M that you know for sure is stock.