I have had my VS Commodore V6 wagon for two years now and have tried everything I can think of to lower the fuel consumption from the 20 L/100 km I get. I’ve changed the throttle body, the idle air control valve, coolant temp sensor, throttle position sensor, and both oxygen sensors. None have had any effect, so last week I replaced the injectors. I thought this would do the trick, but after I filled up this morning, I calculated my fuel usage and I’m now getting an unbelievable 23 L/100 km. The car starts first time every time and runs really well. I don't know what else to do, so if you can help, please do.
Check the air/fuel ratio to see if it’s running rich. I would guess it thinks it’s running cold, but as you’ve changed the oxygen sensors and the temperature sensor I would focus on the ECU.