Abstract: A device and method for installing a device for improving the fuel/air mixture in internal combustion engines with or without a fuel injection system. An intermediate member operatively dispositioned between the engine intake manifold and the intake port comprises at least two helically twisted blades attached to the inner bore of an intake port opening in the intermediate member; these blades are angled in relation to the fuel/air flow path and twisted so as to impart a swirling to the fuel/air mixture. In fuel injected systems, the swirl is imparted to the air flow just prior to encountering the umbrella mist injected to the intake port by the fuel injector. The swirl mixing of the fuel/air improves engine performance, reduces pollutants, and increases gas mileage. Further, in fuel injection systems, the device reduces or eliminates the common occurrence of a burned intake valve caused by a clogged injector.