Found a interesting Dyno Test stock vs aftermarket Filters

http://www.e90post.com/forums/showthread.php?t=137667

 

FWIW, I replaced my BMC filter with OEM and can tell absolutely no difference. I think the aftermarket filters are a lot of snake oil when it comes to our cars. I've read on here that someone dynoed a 996tt with an OEM filter and then without any filter at all and there was no measurable difference.

 

When you do not use the stock air box you only can use a aftermarket air filter.. Maybe thats what drives people to use them? Most stock air boxes don't flow so well either. I pick up 1 psi of boost just by removing the front of the stock air box running gt3076 turbos.