They are very common here in New Zealand buddy, they are not rare in australia at all. why dont you take the car to a BMW dealership and find out for yourself. Even if there are 14 of them, they are only a body kit and other appearance items, the engine is identical to a non sport, and as such your filter is the same as every other of the 10million+ M50B25s in the world. your parts guy is a joke.
just a heads up