Reasons of low millage.
1. Ignition timing is below 20 degrees before top dead center. (only the engine diagnostic management person can tell)
a. it causes loss of power as well
b. it causes a bad sound of engine like its under stress
c Eventually more fuel
d. black carbon on exhaust
e. black spark plugs
One bad parameter can cause multiple issues .
Sudden push on throttle effects
a. it drops the ignition timing to default , that is start time timing , consumes extra ordinary fuel , discharges CO which is un burnt fuel
in reaction the ECU reduces the injection and power loss occures and the driver thinks that engine has gone week
b. Taking the engine RPM to high limits like changing gears at or above 2000 RPM withou reason but for pleasure.
a. low air pressure in tires
b. Breaks jamming on wheels even when not applied
c. high speed Air resistance is directly proportional to speed
d weight in the car.
Get rid of all the above.
Get the timing checked and adjusted to 20 BTDC the engineer know's how to do that toyota or any other reliable shop
Correct tyre presure.
Love your car and drive it in the most decent way possible The car loves a good master.