The manifold absolute pressure sensor (MAP sensor) provides the vehicle’s ECU with information about the load of the engine. In other words, how hard the driver is pressing on the accelerator pedal. An engine works harder (more load) while going up a hill than going down.
The ProTuner controller makes the vehicle think it is always driving down a hill, therefore requiring much less fuel. It also balances out all the signals of the fueling system, maintaining full engine performance and preventing the “check” engine light from illuminating.
Engine performance is maintained because HHO improves the combustion efficiency, therefore less fuel is required to achieve the same power.