Try changing the gas pedal. The gas pedal and throttle position sensor are buil together. That fixed my problem of engine power reduced on 2007 Impala.
Put your key in and turn halfway position
Slowly for a four count Press gas pedal down and let back up
Turn key to off then start car
If that doesnt work you may need a new Throttle Position Sensor
Slowly for a four count Press gas pedal down and let back up
Turn key to off then start car
If that doesnt work you may need a new Throttle Position Sensor