Reference: Fantastic green rally 2008, Bangkok Post, November 23, 2008
Driving a car with the "pedal to the metal" means that the accelerator has been pressed all the way down and that the car is travelling as fast as it is capable. This kind of driving is not fuel efficient and creates road hazards besides. There is nothing green about it. Incidenally the word in this phrase is pedal as in the gas pedal and not peddle, a word that refers to sellling trivial items or things that require salesmanship.