throw out that tornado thing - you've just blocked airflow to your engine - not good...
modfying a car will not improve gas mileage - try making the car lighter, remove spare tyre, rear seats, junk you dont need etc..
oh, and be light on the pedal - here our gas is still twice the price of yours, and its said if you want good economy, drive like theres an egg between your foot and the pedal!