Dinan Performance Chips take full advantage of 91+ octane fuel unleashing additional power from your BMW M5 E34 by recalibrating the ignition timing and air/fuel mixture parameters of the engine management system. Furthermore, the performance software safely raises the factory rev-limit, providing a broader power band and greater road-speed potential in each gear. Significant power gains are achieved at part throttle as well, providing additional performance where the cars are driven most often.