I have owned a Cuore. Bought it brand new in 2012 and used in for two years, 45K Kms on CNG in extreme conditions and never had problems with it. Then CNG became instinct and the engine was not behaving on Petrol. There was idling problem and the mixture was too rich. spark plugs were always full of carbon fouling, consumption too high and in the morning it used to throw black carbon from silencer.
A good mechanic has fixed the issue. The butterfly in carburetor faded from edges due to CNG making the carburetor unable to control the mixture. He changed the butterfly and now it runs great on petrol. Consumption in now excellent.
I love to take it to rushy areas. AC is great, small Automatic car its perfect for city driving.