ISUZU RODEO ENGINE POOR MILEAGE

Hi, I Have An Isuzu Kb240 Le Uses An Opel C24se Petrol Engine. I Only Get 2.5km Per 1liter Of Petrol. Water Goes To My Petrol Tank From...

I Recently Changed My Spark Plugs & Connectors. I Also Changed My O2 Sensor. My Fuel Milage Has Dropped To 12 Mpg. New I Used To Get 20...

If I Update The Ecu Would It Have The Recent Fuel Map And Would It Increase Mpg Presently Makes Around 18. And Were Could I Go To Have It...