Abstract: A performance improving means for an internal combustion engine having an intake manifold, a carburetor and a vacuum intake between the manifold and carburetor, including an upright vessel having an air inlet and an outlet opening in the upper portion, a tube connecting the vessel outlet to the engine vacuum intake, a vertical tube within the vessel communicating at the upper end with the vessel inlet opening and the lower end terminating adjacent the vessel bottom, a valve connected to the vessel inlet so that the rate of flow of air into the tube in the vessel may be adjusted, and a water emissible liquid within the vessel, air being drawn into the vessel through the valve and tube and out through the bottom of the tube bubbling upward within the liquid forming a vapor which is drawn into the engine intake manifold.