I'd try to get out of the deal. For insurance to total a '06 X5, there had to be some pretty serious damage. I'm guessing at least $20k which is a lot and not just for airbag deployment. If you still want to buy it, find out EXACTLY was damaged and replaced and then decide if you are still willing to purchase it. You NEED to get a PPI and prior to purchase. Good Luck with your decision/purchase.

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'03 Carbon Black M5
'04 Silver X5 4.4
'04 MB SL500