I have the turbo XS type H bov for the recirc function. The BOV is still pretty damn loud after I recircluated it and I can still hear it just fine inside the car. You can use them on low boost but you have to pack washers in there just right or it will cause compressor surge or open under boost.
It uses a thick spring to keep it closed but it doesnt put much tension on it to keep the BOV shut. Pack some washers in there and that will keep it shut. I packed 4 washers in mine because it was opening up under boost. (15 psi)
The only problem I have with these BOV's are the way them mount. Its basically a 1" round fitting that you weld onto your IC pipes (hot or cold) then the BOV slides over the round fitting and is sealed on there by ONE little rubber O-ring and 3 small hex screws that easily strip out.
I had constant problems with that damn O-ring leaking and stripping out the small hex screws that I just put some rubber silicon around the O-ring and drilled out that stripped hex screws and replaced then with bigger & better bolts. That solved the problem....
If I buy another BOV it will be the HKS SSQV.
You can hear the BOV in these vids.
http://media.putfile.com/ka24e-t-t3-sup ... 4e...er-60