[Johnny Mullet]

The way mine operates is kinda weird, but I have it figured out and use it to save gas.

Starting the car, the gauge reads about 15 at idle and as you accelerate the vacuum drops and the gauge can read almost zero at hard acceleration. During upshifting, you can actually watch the needle slightly raise in vacuum right at the ideal shift point and it's pretty closely timed with the dashboard shift light. When letting off the gas, the gauge will read around 20-25 depending on speed.

Once you are up to normal driving speed, it's up to you to find the sweet spot. On my particular setup, I get the best fuel economy at around 55 MPH and the vacuum gauge reading around 10 on the dial. I try to keep it there steady. The gauge is sensitive and will change with throttle position/load. I use this to keep a steady throttle position to save fuel.