The syanpse DV works completely different than other valves and the drivability is completely different. The unit is actually somewhat open during idle. Which at first seemed a bit odd, but then after thinking about it, it does have several benefits. The unit allows the system to breathe and by passes the turbo in high vacuum conditions.
On a standard BOV/DV, when you tip in on the throttle there is a sharp and brief increase in vacuum as the engine attempting to draw in more air, yet the turbo has not filled the charge pipes yet. This causes a delay in throttle response that many forced induction cars see.
With the synapse DV the valve reacts and opens to balance the system pressure during these drastic changes in pressure. As soon as the pressure from the turbo enters the intake manifold the valve closes. The reaction time of this valve amazing. Since the valve seat and all the internals have o-rings the unit is complete sealed in boost and can hold 60psi (per synapse).
Although I'm not running this on a subaru, I have noticed the drivability is much better then the heavily preloaded greddy valve that came on the car. Smoother idle, no surging, better throttle response, better throttle transitioning, and no flutter. I may actually run a stock lgt valve to compare.