I recently bought MR wagon 2007 WIT I am facing low mileage issue. Took my car for tunning; replaced Spark plugs, Air filter and cleaning of throttle body. It impacted less than 10% to improve performance and fuel efficiency. After few days, got it's oxygen sensor bank 1 replaced as it was defective. Catalytic converter and fuel pump/filter also got cleaned. It impacted around 10 % improvement in efficiency and economy. I can now get 10 to 12 KM/L in city. I believe this to be poor performance from a 660cc car. What else should I do to increase fuel economy and performance as the vehicle is under power after 130000KM on odo meter.