Abstract: A fuel delivery system for use with an internal combustion engine includes a fuel delivery device such as a carburetor 12, or a throttle body or port fuel injection fuel regulator 16, a fuel vaporizer 14 that provides the carburetor 12 with vaporized fuel, a fuel regulator 16 that regulates fluid characteristics of the fuel, and an electronic control module 18 that controls the fuel regulator 16. The fuel delivery device includes a body 22 having an inlet port 28 and an outlet port 30 and a throttle valve assembly 24 that regulates the air stream flowing through the body 22. The throttle valve assembly 24 is adapted to induce a vortex in the air stream, and to release vaporized fuel into the center of the vortex. An actuating mechanism 46 causes two vanes 42 and 44 to rotate in opposite directions, which induces the vortex.