Abstract: A pulse width modulated controller for N.sub.2 O and enrichment fuel delivery includes a system control logic section which processes signals from sensors for throttle position, engine speed and a number of other user-selectable parameters and a driver section controls electrically operated injectors or solenoid valves. The driver section allows the injectors to open only when all of the parameters sensed in the control section are met. Moreover, the driver section activates injectors according to a pulse generated by a pulse width modulation section which determines how long the injectors will remain activated. The pulse width modulation section receives signals based on the present throttle position and engine speed and adjusts these values according to values for N.sub.2 O and enrichment fuel based on engine speed and throttle position set by the user in a tuning section and thereby continuously provides the driver section with a pulse having a width proportional to the proper amount of N.sub.