Best car on CNG in Pakistani Market is Liana with company fitted CNG. Performance along with mileage is amazing and the best feature is that the car automatically switches over to CNG when engine has attained a specific temperature. Take your car to Suzuki showroom and ask them to perform a computer check where they will fine adjust your CNG kit.
Liana is 100 % recommended with company fitted CNG and if you don’t perform the periodic maintenance then what do you expect. Even cars running on Petrol can even go bad.