BOV and vacuum - help clarify please?

[kinger]

I am on the hunt for a 2nd BOV that will go between the turbo and SC. I don't have a problem as of yet but I think with the way I chop the throttle in tight trails the way I like to, I thought it would be good to alleviate the pressure from both blowers instead of just up at the TBs post IC. Also noticed when I let off even at low boost (17psi) it really spiked the MAP so with plans of being near 28 psi on meth I figure this is a smart move to help keep boots and stuff from blowing off. I am worried about the head intake boots blowing off, I did use yamabond on them when I put the new motor in and that trick does work. The rest will have quality clamps on it and should hold up fine.

Leaning towards this one:

GenV RacePort BOV - (Black)​

The Turbosmart RacePort is famous for being an amazingly small and light BOV for turbocharged competition level engines. Featuring our unique collar design and internal flow structures, it is 50% lighter and 25% smaller than the competition while flowing 330 CFM – making it the highest flowing...

www.turbosmart.com

Curious on the vacuum to pop it off, looking at the data logs from my sled and I only register about 20 inHG and this looks like it needs more vacuum at 18 inHG and that is the most sensitive spring you can get.

But then I look at my current BOV:

Maxflow Race Bypass Valve​

Our Maxflow® Race Bypass Valves flow 320 CFM @ 8 PSIG and feature a compact design that is ideal for sport compacts and other applications with tight engine compartments
vortechsuperchargers.com

And its saying it opens at 10-11 inHG which I am not even close to (according to the data logs but maybe I am not sampling my MAP sensor fast enough to see the low numbers) and it opens just fine.

I guess I am a little confused why you wouldn't want ANY vacuum to pop it open, with the spring options on the turbosmart what am I try to prevent form it creeping open under pressure? Any thoughts? Just a little confused what I am looking for here.

Thanks!!