I have Vitz 2003 model. I have a problem while driving in CNG. The problem is that on CNG with AC, the break gets hard on slow speed and without AC it works fine. I am not sure that this this is the common problem in Vitz or it is specific to my car. Also max mileage of my car on CNG is 112 KM with 50 KG cylinder. Is it perfect or it should be more than that?