Originally Posted by Kim Schwartz
There was still a paper filter behind the gauze filter. Is that supposed to be there or should it have been removed when the new filter was installed?
That second black filter is the permanent Charcoal Filter. Many people choose to cut it out since it is molded into the air box and is only there to prevent some emissions particles. The e39 m5 first had it and people would always remove it on m5 msg boards
Look up info on it on e90post.