i cant speak about a Synchronic Synapse BOV but from "my" personal experience a standard open/close, on or off BOV will not cause idle issues!! it cant, it physically can not unless it is malfunctioning and or the seal is broken. (which can happen on any valve! even stock BPV valve!) all it is, is a valve that is shut 360 degrees around the valve with a vacuum line attached to the intake manifold. if everything is shut, closed and sealed properly, then it can NOT cause an idle issue period!
MOSC your right about everything you said about 100% BOV. the only thing is the "dont need and shouldnt want part". just to clarify 100% back to intake BPV's are needed and you were talking about 100% BOV's.
i promise from my tuners personal experience there is a limit to the stock BPV. does anyone know for sure? no theres no way to tell. just like 5 speed trannys. there is no set number to not go over so you dont blow your third gear. the stock BPV can handle higher boost then stock. but for how long? no one can answer that. everything will break down, everything will need replaced eventually, and time and time again my tuner has had to cut a tune short for going to high on boost and the stock BPV leaking early and making him lose power. the internal spring wasnt made for plus 18psi boost. can one BPV handle it? yes. can all of them? no.
its better to be safe then sorry. to be on the road or on the dyno and have your stock BPV crack or leak and cause a major problems. it has happened just like 5 speed trannys blowing but it doesnt happen all the time.
back to 100% BOV's im i wrong in saying you can run them and run them fine as long as you move the MAF sensor out of the intake before the turbo and move it after the turbo before the throttle body??
Scott-2011 WRX 335HP 394TQ 93 VF52!