Yea, that filter does get dirty. It takes quite a bit of time tho, unless you live in real dusty climate or drive within those conditions. I've cleaned them and even replaced them. I still have half a dozen or so on the shelf I purchased in bulk off ebay lol. What I've been trying to figure out is why they buzz after shut down. Even completely new, they still buzzzz...

 

vacuum should drop alot when you first crack the throttle open