FWIW I have the RKX based on RZR Joe's write-up, plumbed to recirc, and it sounds more like feeble Ric Flair than Psssht. I was actually wondering if I screwed something up on mine but the machine runs great with it, making boost where it should.
Ironically, I DID screw up initially and install it backwards, and heard absolutely ZERO sound at any point, but the machine still ran great?! I even have a data log file from that run that I had Mike look over and he said everything looked great.
I don’t know if this applies to the OP and his AA BOV or not.... but I setup my RKX to vent to atmosphere after I read this thread because I was curious, sure enough, feeble Ric Flair was riding with me.... I only rode once like that, but I recently decided to adjust my wastegate so I could run the AA stage 3 tune I have if I wanted to.... I didn’t do it to get rid of the Nature Boy, but I found out, that it changed the BOV sound to the loud “psshhh” you would expect. This was the only thing I changed, Still currently on the same tune as before the adjustment, and that was the only thing in the entire intake/boost/engine I changed that could effect it.
My theory is that my wastegate wasn’t adjusted correctly to begin with, possibly due to my elevation (6000’) or just being tuned in general ( Even tho not a big enough tune to “require” an adjustment ), but I had always noticed (visually, by time/duration/shade of Turbo glow, even after the cat was removed ) that my Turbo was running hotter than I felt it should, because it was being a little overworked to maintain boost, because the wastegate was opening too soon, the feeble BOV sound was due to it partially venting out of the wastegate, and not holding the boost in the charge tube like it should, now that the wastegate doesn’t open as soon, the boost stays in the charge tube, like it should...so “pssshh!”
(Side note: I couldn’t remember where this post was, who was in it, or when it was really, so I found it by doing a forum search for “Ric Flair”.... which I found pretty hilarious )
-Give it a second... it had to go to space and back first ( Sent from the lifeline that is my iPhone XS Max )