High fuel consumption

The Mass Airflow Sensor fails on these sometimes and could cause high petrol consumption. Try cleaning it with an approved cleaner. While you are at it, clean the throttle body as well (with throttle body/carburetor cleaner). Finally, have the fuel pressure checked. Low fuel pressure can cause excessive fuel consumption.
If you check engine light is on, have the computer scanned and post the codes here it you need further assistance.