If your vehicle is equipped with this gage, it is located near the driver's side of the instrument panel cluster.

This gage indicates vacuum during light to moderate throttle and boost under heavier throttle.

The gage displays the air pressure level going into the engine's combustion chamber.

The gage is automatically centered at zero every time the ignition is turned to RUN. Actual vacuum or boost is displayed from this zero point. Changes in ambient pressure, such as driving in mountains and changing weather, will slightly change the zero reading.