yar come on! my cultus 2011 is doing around 200 kilometers in a tank. it costs me around 600 to have it filled up.
Have it checked up from Federal Motors. Zoom/Focus CNG are good options to have your tanks filled up in super and blue area. check the gas pressure and see whether you are getting 190 to 200 bars on the meter. What i can say is that you must be refilling at a pressure of less than 150 bars....
check one thing more.... does your car lessen its cng pressure while standing idle (engine off), in that case i shall suggest you to check it for a leakage.