A regular lambda probe measures the amount of oxygen in the exhaust gases and sends a signal to the injection carburetor to correct the air and gasoline mixture, according to the probe's measurements, which will typically aim for the most environmentally friendly mixture.
With this emulator from Polini you can trick the ECU on your 4T scooter into thinking that the mix in your system is exactly as it should be.
The emulator is plugged into the socket where the original lambda sensor would be connected, and this is how the motor control is told by the emulator that it measures the most optimal factory values. But in fact, the values are calculated to provide better performance, resulting in an optimization of the performance of your scooter.
Polini recommends using this lambda emulator in collaboration with their HI-Speed variator for Yamaha 4T scooters
Note: Fits only models with lambda probe in the exhaust.