The BMW swirl flaps problem. After how many kilometres do they fail please? Are they relatively easy and cheap to replace?
Can't tell the exact mileage (it depends on how the car was driven - city or motorway driving), but THEY ALL FAIL EVENTUALLY
The flaps are disintergrating from metal fatigue. BMW addressed this problem in 2004, by introducing stronger metal fixings, but they are known for failing, too. So in 2009 BMW got rid of them completely.
It's an easy fix if you can do this by yourself (takes a couple of hours). To get access to the flaps, the whole intake manifold has to come off. They are not replaceable - you have to buy NEW intake manifold from BMW. And that one comes with the same flaps that will eventually fail again
So people (including me) are just ripping them out and blanking the holes.