Blow Off Value???

I'm about to purchase the ultimate racing turbo kit for my S2000. It comes with a HKS Super Sequential Blow off value. I went to check out a car with the kit installed running at 7psi. You can barely hear it... and only when driving in boost. I was hoping to hear something when I rev the engine. Any advise of which bov to get? I was expecting a sound like fssst sound. hahaha

thanks guys