gas mileage dropped from 31 to 24 to 22 ,mpg. Happen to anyone else?

I don't have my workshop manuals with me. If that engine uses an airflow sensor on top of the air filter housing held on with two screws that type of air flow meter on Toyotas used to fail, set lean trouble codes result in loss of power and lower fuel mpg. With the sensor cold try CRC product # 05110, (any auto parts store) don't use anything else it will damage the sensor. A scan tool is needed to really test the sensor air flow.