BMW use there ''M'' division for performance parts. So a filter from an M3 would be classified as a performance part. I know you dont want to use ''outside'' parts but K&N are really very good filters and even have a 1million mile guarantee. Just by taking away the filter box and fitting an induction kit you are making the car less original regardless of using BMW parts.
The ONLY Hellrot Red 323 in the world, emmm except for the other few thousand dotted around the world.