Last year i was very much into this matter because of newly learned driving.
There is actually a little bit differnet way to drive an EFi car. I hav seeen most of the people who used to drive CARBY engine car in daily driving and whenever there is chance of driving an EFi vehicle, by mistake they turn it off. But they never did it in CARBY.
EFi is responsible for BETTER THROTTLE. I would like to mention here that on HIGH RPM it is excellent but YES this is TRUE, at low RPM there is a LAG.
It really depends on driving style then. U hav to be well fimiliar if u want more from the EFi, else it is rubbish for the layman.
Coming into the point i personally hav SANTRO. Never had a chance of running the car with KHYBER but i rate SANTRO 1st on CNG then CULTUS and then ALTO.
CULTUS also do pretty well but on CNG it can't beat the SANTRO.
KHYBER is actually the best when there is a matter of SUZUKI.
Well i will really appreciate if some bady can post their specs here, so that all mysteries should be cleared.