Genuine OEM Audi Engine Control Unit, part number 4E2990990. This is the primary computer responsible for managing all engine operations, including fuel injection, ignition timing, and emissions control. It receives data from various sensors and sends commands to actuators to ensure the engine runs efficiently and within specified parameters. Genuine OEM ECUs are pre-programmed with the correct firmware and calibration specific to the vehicle's engine, ensuring seamless integration and reliable performance. Incorrect or non-OEM units can lead to drivability issues, check engine lights, and potential engine damage.