that sounds retarded... are you saying that if your CBV doesnt vent at Idle and low boost levels, youll get surge??? tahts 100% wrong. see, the nature of a CBV/BOV is to open when under vaccum. At idle, your engine produces vaccum, which normally would make the CBV open. But, you dont need/want it to vent at idle. its not something you should be Shooting for or get all upset like "Godammit, why isnt my BOV venting at idle?! mother fucker!". The amount of vaccum at idle is ALWAYS less than the amount of vaccum during engine decerlation (during a shift, engine RPM's dropping when clutching, or deceleration in gear). If you are good/smart, youd fine tune your CBV to be open at maximum vaccum, but be closed at idle vaccum. a WELL tuned CBV will be closed at idle and open during max vaccum, IE: shifting, coasting in gear, clutching. the reason why MOST CBV's do vent at idle as it stands now, is because every motor has a different vaccum level at idle... some cars, its 20 in/hg, other cars its only 18in/hg. so a car that has a CBV that vents at 18 in/hg, and IDLES at 18 in/hg will be venting... id suggest tuning the spring tension a little tigheter so its closed at 18 in/hg, but opens @ 19-20 in/hg. that way, anytime the throttle is closed and the engine RPM's are anywhere above idle-speed, the CBV will be open cuz the vaccum is greater than normal Idle vaccum.

thats just my impression.