Htr / Air controls do not shift the vents - Vacuum issue?

Since we'd be hunting for space to put a Tank where there isn't one already, I'd suggest this one for $13 on Amazon. I used this "two way" check valve, meaning it served as a Tee and a Valve.

There's another Dorman Vacuum Tank that might have the Check Valve built in. I chose the one where I could use a separate valve that incorporated a Tee (to supply the Tank and the HVAC Controls). Either way, it takes a Check Valve, a Tee, and a Tank.

Tank is pretty large. Check Valve has to be first. Engine vacuum source, then Check Valve. Then the Tee. One line from Tee to Tank, other line from Tee to HVAC Controls inside the cockpit.