well City 11....
i would agree with recommendations by everyone "NOT" in favor of CNG. And like many said, its milage will keep on optimizing when you reach 5000KM on the odometer. I usually pre-heat my car before putting it into D (drive) waiting for that blue cold engine light to turn off. Even then it gives me 11.8 Km. Also its running on 195 width tyres (stock size is 175).
You may get a good CNG kit (lets say you go for the best i.e. Gas Injector Kit or OMEGAS by Landi Renzo) that would have a great pick-up but it would cost you 75k minimum. Also you would be sacrificing on engine warranty, Monday-Tuesday Gas Load Shedding. Plus long queues.......Think abt it.....You didnt spend 1.4 million for nothing.......Enjoy it.....Rest is your choice.....