I strongly believe that u should contact @LOGAS as he is the right person for CNG. He would definitely give u the right advice and has one of the best kits available.
I'm in Islamabad and using my vitz automatic on CNG (without Lambda) for more than a year. no real problems except some difference in pick-up while A/C ON as compared to petrol. another pakwheeler got CNG a few days ago along with the Lambda controller and he is more than satisfied with the performance.