@Saadisb..........
To be very honest the efi kits are not a proper solution, secondly the mixer (ventury) is the main part which plays the major role for the gas consumption and air/fuel ratio, mostly installers dont know the theory or the working of mixers, they just install the components without knowing its working principal or the mechnisum, in most of cases its just need to set the injector pipe of that mixer to its right point or to set its size, which counts a lot for getting the best possible air / fuel ratio.
3rd part is the condition of air filter, we have a lot of dust in our country, cleaning air filter once in a week and change the air filter after about 2/3 months is recommended, depends upon the area, city and travel routs and drive style.
4th......has any installer knows about the btu values of gas in ISB/LHR/MUL/KHI......its another issue to set the mixer (ventury) seting........So, the conclusion is we need education....same like in other fields we also hv lake of knowleage here too.