water injection and engine vacuum question

[lunarhighway]

i have a few questions regarding engine vacuum, as i'm trying to come up with a basic water injection system for a naturally aspired carbed engine.

i'm trying to design something similar to Ron Novaks design, but with the inlet above the butterfly valve so that there's most water coming in when it's needed.

my main question is: what is the pressure there? i assume most vacuum is created below the throttle... since i rarely use full throttle i'm affraight the pressure above the valve is not low enough to suck up enough water vapour?

on the other hand i thought perhaps it's a good idea to use a mini ram intake to pressurise the water reservoir... might help generate enough presure difference to get things going.

any tips or corrections are welcome.