ECU Tuning refers to the process of modifying the software in a vehicle's Engine Control Unit (ECU) to enhance performance. The ECU is responsible for managing various engine functions, such as fuel injection and ignition timing. By adjusting these parameters, tuners can improve horsepower, torque, and fuel efficiency. This tuning can be achieved through various methods, including chip tuning, where a new chip is installed, or remapping, which involves rewriting the existing software. While ECU tuning can lead to better performance, it may also affect vehicle warranty and emissions compliance, so it's essential to consider these factors before proceeding.