Mine did this also, it kinda sounds like a SSQV except quieter due to recirculation. Mine did this from the very point that i bought the car so i don't know if it's abnormal or not. I do know this: I took my cousin's cooleze upper hardpipe portion off of his car and put it on mine since his isn't running (I like to get a loud POP! (backfire j/k) right after i let off the gas and get the SSQV to go off). Funny thing is, the BOV sounds completely dif on my car than it did on his, the only difference was I didn't use his full kit because the lower pipes are a PITA to put on and take off. The BOV on his car would make the fluttering noise under low boost. On full boost (stock) it would let off the normal BOV sound. On my car it doesn't flutter under low boost (also stock setting), it makes the really high pit BOV sound. Plus it's actually ALOT higher pitched on my car than it was on his. It could be because i'm running half an exhause (lower back pressure than my cousins) whereas he's running a complete system (I haven't bought the catback portion yet). I'm also talking about the HKS SSQV BOV from the Colon down (no pun intended).
