Since a Map Sensor Enhancer is obviously a expedient that works in conjunction with the Map Sensor we should have a quick look at what that device's function is.
Map stands for Manifold Absolute Pressure and this expedient absolutely measures the vacuum in the intake manifold of the vehicle. The level of the vacuum in the manifold changes depending on the load on the engine. This data is transmitted to the on board computer and is used, amongst other things, to regulate the air/fuel mixture.
Manifold Absolute Pressure Sensor Problems
So what is the problem? Well the on board computer is pre-programmed according to distinct standards and, amongst other things, is trying to avow an air/fuel composition of 14.7:1. This is regarded as an optimum ratio but does not take into catalogue that distinct fuel saving techniques employed today requires a ratio with less fuel and more air (known as a lean mixture).
For instance when any of the so-called water fuel technologies are employed the intake air is enriched with hydrogen and oxygen and the best fuel saving is achieved with a lean air/fuel ratio. If the on board computer is allowed to add fuel to accomplish it's optimum composition most, if not all, of the benefits are neutralized.
The Map Sensor Enhancer is employed to remedy this situation. The wire that transmits the signal from the Map Sensor to the on board computer is cut and the Enhancer is associated so that the signal now goes straight through the Enhancer. Since a higher voltage signal indicates to the on board computer to increase the volume of fuel in the air/fuel ratio, it is a simple matter of employing a potentiometer to sacrifice the voltage in the signal.
Since driving and even atmospheric conditions affects the "ideal" mixture, the Map Sensor Enhancer is settled so it is accessible while driving and fine adjustments can be made for various situations.
I hope that this clarifies a few things and is of use to you. It should also be noted that various other devices, also a Map Sensor, are used in different cars and those would wish slightly different techniques
Map Sensor Enhancer - How Does This Save Fuel?