I was in the same situation as you (sound/quality). 1st Sound: Vitaly my mechanic and owner of Pit Stop Performance (the shop next to COZ here in Arizona) pursuaded me to go with HKS as opposed to the Turbo XS which I was leaning towards. He has the HKS valves on his Z (which is "sick") and will be in sportZmagazine this year. While the HKS BOVs are not as loud as the TurboXS they are definately loud enough to grab big attention and the high pitch is a lot more "race like". 2nd Quality: I dont think there is any question that the HKS SSQVs are the valve of choice around here. I know some will disagree about worth of BOVs but for one I installed Garrett GT28RS turbos this summer and the HKS BOVs difinately improved my lag time. That alone was worth it to me. I have had them on for less than a week so I'm sure I will find many more benifits once I get comforatble with them. Just my two cents.
