Hey guys, this is Peter from Synapse, I am the one that designed the Synchronic BOV. I ran across this thread tooling around the internet. I'm only jumping on to chime in on the "rich between shifts" discussion, but I also want to address any concerns you have about doctored videos, etc. So, forgive me for the long post.
YouTube - Synchronic BS Callout 2: Proper TiAL setup on Low Boost
This isn't some random guy's video, this was made by Jake from Tial. Watch how the valve floats after discharge. That spring in there is way lighter than what they have in the instructions.
The Subaru in our videos was run in identical conditions. The Tial does blow, off, but only after a certain boost pressure, regardless of RPM. The point is that the Tial will flutter at anything below that boost pressure. Which, for reference is what you're doing daily driving anyhow. You aren't doing WOT full boost in every gear on the way to get Dunkin D.
Watch this video, you'll clearly hear the Tial discharge at full boost. You can also hear it surge after it discharges:
YouTube - Tial vs. Synchronic BOV
This video was cut shorter, since people have a short attention span:
YouTube - Synchronic BOV Subaru WRX
The fluttering sound you hear on the Synchronic revving at idle is the anti-stall flapping at low air flow rates, not compressor flutter.
Why does the Tial work this way? Because it is designed to stay shut at idle, not open up at all boost pressures. Why do you think that they have you match your vac level to a spring? The car was setup per their instructions. Bottom line, that same spring pre-load pressure needs to be overcome in order for the BOV to open up. So 11 psi spring, means that you're surging at anything below 5 psi. Why 5 and not 11 since it is an 11 psi spring? Because you have to factor in the vac pressure on the diaphragm + boost in the pipe pushing on the valve face = 5-7 psi. The Tial works as designed. You can run a lighter spring, but as many find, the performance and response is just not as good.
Now, regarding rich between shifts . . . I experienced a weird scenario the other day with our test Evo when doing more testing. We did vent to atmosphere without our anti-stall and didn't have any problems, but on a Subaru you will have problems because it runs differently. Now, the interesting thing is that we ran it in one configuration (Port A+B for vac) where the the BOV was open more at idle and it ran sloppy and ran like it had a leak past the MAF. But then we ran it in another configuration (Port B only) that didn't have the valve open so much, still VTA, and it ran with absolutely no problems. First and foremost, we recommend everyone recirculate on a MAF car, especially a Subaru. But, we're actually going to run this test next week ourselves too on a Suby.
All other BOVs on the market, based on the geometry I've seen, are all designed to just dump air flow upon opening. The Synchronic is actually designed as a flow regulator. So, for the engineering types, the valve position is different based on the level of vacuum, so it follows the changes in the intake manifold to the T. And flow rates are designed to be linear, with regards to valve lift relative to seat, assuming subsonic flow.
We'll let you know what we find with testing. Also, Tampa is far from Miami, but there is a dealer there NipponPower.com where you can go, try the bov, just to try it. This is how confident we are with the product.