Stage 4 Engine Software is for use with the High Flow Cold Air Intake, Throttle Body and Air Flow Meter, ensuring optimum performance and drivability. Dinan Performance Engine Software unleashes more power from your BMW 540i E39 by re-programming the fuel mixture and ignition timing parameters of the engine management system. Furthermore, the software safely raises the rev-limit, giving your BMW a broader power band and greater road speed potential in each gear. Significant gains are also achieved at part throttle, making extra power available where you spend the bulk of the time driving. The top speed governor has also been eliminated, enabling the vehicle to achieve its natural top speed.