I have a 2007 JDM Alto with 50K kilometers. Recently my fuel average has dropped to 11KM/Liter in city driving with the AC on. Also I have noticed that it does knock a bit with the AC on, and feels like its under load, but never knocks without the AC. I am using regular fuel, no hi octane. I have cleaned the spark plugs, put in the injector cleaner fluid, new air filter and gotten the throttle body sprayed with the carb cleaner. Still the mileage is the same. The only thing left is the catalytic converter in my opinion, though its not showing other tell tale signs of a choked catalytic converter. Any suggestions?