The Twin Tuner allows you to easily adjust your fuel injection to match the requirements of performance parts including camshafts, free flowing exhausts, and low restriction air filters. You can add up to +30% or subtract down to -20% fuel. You can use the mode and up/down pushbutton switches to make fuel trim adjustments in the RPM and throttle position ranges required by most applications. The fuel trim value is displayed on a bright daylight readable LED display. The Twin Tuner also has an advanced mode, where you can use the optional USB Interface and PC Link Tuner software to make precise fuel adjustments. The USB interface also allows you to make independent adjustments to the front and rear cylinders.