If you're serious about tuning your car, the best thing to do would be to take an ECU tuning course. There are courses available in many different countries and you'll be given professional instruction on successfully tuning an ECU. The first thing you should learn is what ECU tuning and remapping is. It's when you alter the settings and different parameters of the ECU in your car. This is done to optimize and improve them to create your ideal performance. It's commonly done to increase the fuel economy, the engine's power and handling, and other things such as the removal of a speed limiter. You can also learn the art of ECU remapping by searching online. There are lots of resources that you can take advantage of, as well as many books on the subject if you enjoy reading. Another thing to remember before you throw yourself into ECU tuning, is you need to know the fundamentals of how your car works. Trying to perform something super technical such as ECU remapping before you learn the basics, is a disaster waiting to happen.