Adding a spacer allows for power increase in the low to mid-range for both engine torque and horsepower. Most spacers are CNC machined from billet aluminum for accurate fitment and the unique bore design creates a votrex to the air entering the engine. They are suppose to improve fuel mileage-save gas & gain power. *This is the so-called text book definition for a throttle body spacer!
btw. throttle body spacers are only useful on a carbed engine, if you have EFI you are throwing money down the toilet so to speak. They give NO increase on a fuel injected engine.. but apparently on carb'd engines they do.
