The POWERAID Throttle Body Spacer is designed to enhance off-idle torque from 800 rpm to approximately 3,000 rpm. The spacer utilizes it's unique, patented Helix Bore design to spin the incoming air charge as it passes through the throttle body spacer. The spinning air action boosts the velocity of the incoming air and contributes to better atomization of the air/fuel mixture as the air charge enters the combustion chamber. The end result is more part-throttle torque and improved mid-range power. This product is legal for sale or use in all 50 states only for 1989 or older vehicles equipped with a 4 BBL Holley carburetor (CARB D-609)..