If your 2005+ car is experiencing some throttle response lag, there is a procedure to calibrate the 2 pedal position sensors. Note: this does not apply to 2004 or older cars.

Throttle calibration ...

1) turn the key in the ON position (don't start the engine)
2) press the gas pedal down slowly all the way down
3) let go of the gas pedal fast so it comes back up
4) turn key into the OFF position
repeat steps 1-4 two more times then start engine.

(procedure kindly provided by gDMJoe)