strange buzzing noise after blow off valve

What is your question?

Stange buzzing sound after the blow off valve. Everything is stock, I fitted a filter on the stock intake piping. The sound was there before I changed the filter but it is now way more pronounce since I remove the restricting box. Here's a video of the sound: www.youtube.com/watch?v=2QmSCR_VRm0

What makes this problem better or worse?

Happens when lot's of boost. (above 10 psi)