Well, I got the Synapse Sychronic BOV in on Friday. I put it on Saturday night and tested it out. If you've ever seen the videos of the BOV on streetfire.net then you'll know what I'm talking about.
The BOV doesn't hang open as far as you'd think it would once vacuum is applied to it, but I'm thinking that I may have a vacuum leak somewheres that needs to be tracked down as the supra does pull a healthy vacuum when operating correctly.
I left it vented for the test that way I could easily hear when it would actuate. You could hear the air rushing into it at idle, so an air filter would definitely be recommended here as you don't want FOB in your engine.
Juice the throttle and it immediately closes. I can't build any boost off of free reving my car so I didn't even try.
Taking it for a drive it does have a unique sound to it, almost similar to a compressor surge sound. However, this was not compressor surge. I thought it was for a moment, so I would stab the throttle a few quick times and the tone of the BOV is a little higher pitched and quieter when not building much boost. It does let out the air without a moment's hesitation. I've ran a genuine HKS SSQV before and I am certain the Synapse is quicker to let off than the SSQV.
Me and my cousin took it down some twisties late Saturday night and the BOV performed quite well I have to say. Even juicing the throttle and then slowly backing out of it would actuate the BOV almost right before the throttle plate fully closed.
The BOV does have a tensioner spring that's fully adjustable, but is recommended not to be messed with straight out of the box, it is set at full soft right off the bat.
I had a little issue with getting the BOV to securly stay in place on the flange (HKS) but I'm attributing this to using the original o-ring and snap ring.
In summary, I give this BOV a 9.5 as nothing's perfect.
I'll almost miss the sound of the BOV once I recirculate it (comes with the recir fitting straight out of the box, the HKS does not).