quiet bov or bypass valves

What are some of the more "stealth-like" bov or bypass valves? I was looking at the GReddy or Tial 50mm valves for T-76GTS head unit on kits from Ohio forced induction or PTK. Are these valves interchangeable b/t turbos and superchargers, btw? I've heard ATI bypass valves are very loud, like a pissed off veloci raptor. I don't want that. I want as quiet as possible. What about Mondo valves? Any suggestions and personal experiences will be appreciated, thanks!

I have a 97 OBD2 PCM 383ci LT1 w/ ATI D1 15 psi pulley set-up. My experience with SC was that I needed to bypass air to the intake of the SC with running the MAF on the intake side. Look @ evolutionmotorsports in AZ. I am running two of their valves (recc from this site). Approx $130 each. They are working good for me. I also ran a HKS blow-off valve, and, converted it to a bypass. Have yet to try it again, but I cannot dump air due to use of a closed loop PCM mode and MAF placed before the SC intake.
Hope this helps.