Vacuum Advance Question

The car should have more power in my opinion, the plugs look decent to my novice eye.
It runs decent without it hooked up, just drinks gas.
I was under the impression that the Allen screw adjusted the amount of vacuum it takes to actuate the canister itself...no?
It seems that one could limit the stroke of any said canister to achieve the desired amount of advance.
Is this a trial and error thing that I need to just keep beating my head against it till it works? lol

It drinks gas, compared to what ? What. is your reference ?