Here's the thread: http://www.z4-forum.com/forum/viewtopic.php?f=7&t=83675
As to what it does, well I don't think anyone is quite sure The idea is that it forces more air into the engine and therefore increases performance. (although Steve84N would disagree, check out his post on this thread: http://www.z4-forum.com/forum/viewtopic.php?f=2&t=85172&start=15)
Finally got round to fitting Dans wonderful air scoop.
Fitted it in about 40 minutes through the grill opening, it was very fiddly but piloting smalls holes into the plastic using a 'Twist gimlet' (a sort of a very sharp bradawl) helped.
I will buckle in tight when I go for a spin tomorrow - don't want all those extra horses overpowering me :driving: