i've heard the type-R BOV b4,it was on one guy's car who bought his VR4 banana manifold from me.....
all i can say is tht the sound was chun man....garang man....got a pic of his engine bay at the thread under the advertisement section where i post my stuffs up for sale,don remember if the pic got feature his BOV or not la,coz the main focus was the manifold ma :P
anyway the sound was nice la....for me it sounds like some diaphragm vibrating with a loud sound....
i remember tht guy told me type-r is mor suitable for high boost application la,can tahan higher boost,type-S for lower boost gua....correct me if i'm wrong,not very sure about this also,coz hear ppl say only,nv do a research myself :0