Two types of flutter, I guess. One is when the spring rate of the BOV is too heavy and closes in the middle of a release event. The vacuum produced by the engine isn't sufficient to hold the BOV open.
You want one psssss on a throttle plate close not pss ps p (Those are technical sounds by the way)
On the flip side too light a spring will cause the BOV to open a little bit while pressurized, letting off some of that precious compressed air. When logged would look like little spikes. /\/\/\/\/\
I think. Someone validate or tell me I'm retarded. Don't make fun of my graphs, I was up all night making them