hey mate, i dont know if this helps at all, but you were comparing the blow off noise compared to your r33 gtst?? big big difference with the way they are plumbed back.. rb20's and rb25's have very short link with the pipe that plumbs it back making a very loud sharp whoosh through the pod filter where as gtr's ahve a very long plumbback pipe across the whole front of the car causing an eco'd muffled blow off noise alot quieter and different to the normal blow off sound coming through the filters
or are you talking bout a totally differnt noise all together?