search for "econokit" designed by germans and there is a dealer/distributor whatever in karachi...
on pakistani website there are pics of cars with econokit installed
actually you may have felt an increase in pick and drivability in rain or humid weather. thats because of water content in air which when used in cylinder to help ignite fuel becomes steam by taking some heat from combustion and increases the pressure in the cylinder.
In short you are making your engine into part steam engine.
Advantages:
1. Less fuel will be required to get the same pressures in the cylinder.
2. engine will run cooler as some heat will be absorbed by water vapours to become steam.
The brand "econokit" preheats the humidified/bubbled air from the bubbler bottle filled with water using vacuum of the intake. the name preheater is given by me and is called A GENERATOR by the maker.
My suggestion:
1. Just use a bubbler
2. the generator(preheater) looks scam to me. it has nothing but a metallic cavity/box tied to the exhaust...
3. an expert can do the tuning on it. the fuel mixture, ignition timing, etc are to be tuned along with the vacuum sucking variation with rpm. as on higher rpm the vacuum dies so no bubbling...
the device cost like 23000 to 25000 rupees...