rocket, our cars are tuned a little further than most capris on here.. your right, above 12-14 id say the stocker is too small to relieve boost surge. but i removed the plastic ring a long time ago and the moo stopped. wether from flow of air not causing the diaphram from fluttering or what does it. it stopped..
and at higher pressures the design of an ssqv, whereas boost holds it closed.. a vacuume signal is needed to override the boost holding the valve closed to actuate it.. whereas say a greddy type s, uses an adjustable springrate to hold the valve closed under boost. and is the reason they can also be used as a pop off valve for setting a max pressure on heavily boosted engines..
an ssqv will not pop off, or relieve any pressure until a vac signal is seen.. you can push 3 bar to it, and it will just push it closed tighter.. where 3 bar would completely open a type s using a stock spring..
so if you are say, driving a road course where you come into a corner wanting a little less power, and you lighten the pedal. yet keep the engine reving and the t.b dosent close to create a vacuume the ssqv will not actuate...
small amounts of surge can occour..
im running 17psi daily.. and mine will do it sometimes.. and i bought my ssqv from corksport. not ebay. it says HKS in yellow right on it...