Originally Posted by andrey_gta
Tes just get the official BMW performance air filter(search for its part code) or the oiled K&N version( ~$40) or the afe version (~$60-$70 for oiled or dry, cost is the same, just use the part number form their website in google)
Oiled could dirty up the MAF sensor, so be careful and know ehere you can buy a MAF cleaner spray. Never touch the sensitive part...
I think i'll have a look at getting a K&N one dropped in and see how i get on with that and then if i'm after more i'll look into cutting a hole (perhaps not as big as the one from the link you gave though!! ha)
Thanks for your help Andrey!