@mansoorkhokhar: I have an Eminent and no plans to install CNG but still can sched some light on this topic. You will not be able to get the Suzuki SIS kit installed in RXI/LXI for your Eminent. @logas imports SIS kits and has a facility in Lahore but the kit will cost you around 80-90k and I think with recent increase in petrol prices the kit may have gone even higher.
Do not install the old-skool CNG kits in EFI cars its a pain if you do not know the detailed working of different components.
However, Suzuki guys only told me to keep at least 1/4th tank of petrol when driving on CNG not mentioning warranty stuff. I did remind me that the car does not come with CNG and finally I had to cut him off that I am not installing one EVER.