Do you guys honestly believe that a cat convertor can choke out? The immense heat in a petrol engine exhaust is high enough to burn off any carbon deposits off it. The only way it can choke is my melting of the core which can only happen if raw petrol is dumping down the exhaust which sets an extremely hot fire in the convertor - it will glow red from outside while it kills itself.
These series of choked convertors I hear about can only be traced to either the engine is running extremely cold at all times or the cars systems were deliberately damaged to get rid of in the country of origin. Please remember these cars are not meant to work for long, they are kei cars - cheap and disposable.
btw - 12.5 km/lit IMO is more than enough for that little engine spinning at high rpm. I used to tell people that small engine in large car does not mean good consumption. Its the opposite. Large engine in small car = good consumption as you are not lugging it around in normal drive. Normal load drive in a 1.6 litre small car is equal to torture drive in kei car.