Brother of The Benz, Joel
If you knew what the manifold pressure was before a leak, then yes it would note a drop in manifold pressure, less vacuum.
This could be something other than a leak in the system; it could be an improper operating engine.
There are many things that the Econo-gauge can detect. It's the awareness of the owner to identify the needle when it is further to the right.
Happy Trails Beep Beep from The Spiderman in Houston!!!