Chip mod for petrol engine

[Basie]

Hi

I have a FJ 79 with the South Arican version of the 4500 EFI petrol engine ( very thirsty). Seems that here is a chip that can be changed or added to the engine management system that will increase power, decrease fuel consumption and save the world. Cost about the present price of 250 l of fuel. People who had it put in claims 3 liters/100 km less fuel consumption. I might claim that as well if I paid so much.

Anybody has experience with these chip mods and if it is so good and without side effects, why not standard?

Thx