For those who are looking for the stealth BOV and need to a filter. I found a $4 lawnmower air filter at ACE (71753 for tecumseh/sears) that slips on the end of the BOV (1-1/8"). All that's needed is to shove a grommet (or any round semi-stiff rubber piece) in one end and seal it up with some RTV. I just made a 50 mile drive on and off boost (8psi) and it's still there. The fit is tight, but the ends are rubber and stretch to form a good grasp on the bov. I was looking for a filter first, the muffling was a bonus. I can just barely hear hint of the valve now. - rob