I have a 50mm as opposed to the Q. They use the same springs, but the springs are rated differently for the two different valves.
I've tried several different springs...a -7psi spring is too loose and leaves the valve hanging wide open at idle. -11psi spring is too tight and NEVER opens, even at WOT/full boost...you get some crazy surge. -9psi spring is just right, but it just barely cracks open at idle. I shimmed the spring a tiny bit with some washers and now it's perfect, stays fully closed at idle and is still very responsive.
For the Tial Q valve, a -10psi spring should be perfect.
This is how you want to adjust or choose the spring in a BOV, and that goes for all BOVs. You want it just tight enough so it keeps the valve closed at idle. Any tighter, it won't open very quickly and you lose response. Any looser, it'll hang open at idle.
For a recirculated valve, you can choose a lighter spring that will let it hang open a bit at idle. It'll gain you a bit of response and it won't matter if the valve is open since it's connected to the intake pipe. But for VTA, you want it fully closed idle.