on this subject of milage tampering.. if you read through the carte blanche report, you will read that the guy turning back speedo's says that not even bmw will know the milage has been turned back..
this is just bullshit, plain and simple. pulling the speedo and tampering with the security eeprom is easy, the programmers are freely avaidible, and cheap. if you read a bit futher down though, to the commentary given by the bmw rep , he says that the true milage is stored in several control units, besides the speedo.
for a tampered car to be COMPLETELY undetectable, the other controllers have to be altered too, which is not at all so easy.. and thus not done nearly as much as the simple speedo "haircut". (last time i heard, to have a car's milage turned back truely undetectable costs in the region of R6000-00 )
which means that in 80% of the cases altered milage WILL be detectable by bmw..