My bonneville Sse get poor gas mileage. Ive replace the tires and air filters spark plugs and got a fuel injection system cleaning and new ignition wires.i don't understand why but if the front of my car is sitting up the gauge shows i have more gas and visa versa.I don'tknow if it's the gauge (other ones work fine)or maybe something else.And the gas door has rusted.also when i start my car sometimes it takes a a crank or 2 longer then moves forward but the car is still in park just the body so help!