That is a weird design in E90, don't have anything like it in my E70 diesel, took apart the air box. I'm running K&N so that helps a little.
Retired: 2005 N52 E90 330i Sport 6AT
Retired: 2007 N54 E92 335i Sport 6AT
Current: 2012 M57 E70 X5 xDrive35D