i'm trying to find the actual article, but can only find reference to it. lots of other forums talk about it, but not found the actual article.
i also added the BMC on there, it is the most expensive, but they make great stuff, and very few people seem to know they exisit. they build a lot for motorsport and F1 teams.
as for cleaning the do luck ones, you can use a K&N filter cleaning and re oiling kit and you can get them from halfords.
In the world of BMWs, the BMC filters are highly regarded. I also had a BMC performance panel filter in my BMW 330ci M sport, bought it for £45