This is very interesting:

Generally there are two ways of doing it, changing the M52 pipework so it'll fit the manifold (ebay kit) or the other is to change the M50 manifold so it is a direct replacement for the M52 original.



You can buy the plate from the bottom of the M52 manifold from BMW, and that will match all your original pipes as they are.

The M50 manifold gets a hole cut in the bottom, and the old idle control valve "input" filled (done here with some white gunky stuff)





Then get some nuts and bolts, nylock/thread lock them, and bolt the plate on, and it'll fit the M52 stuff, like the oil separator etc-



http://bmwenthusiasts.co.uk/forum/viewtopic.php?f=58&t=3882#p44184