I don't want to send you on a wild goose chase, but someone on the fakebook page had a similar problem. It was the throttle sensor/pedal.
I don't know if that's what is causing your trouble. Have your tried the Throttle Reset procedure?
1. Turn the ignition key to the on (not start) position.
2. Press the gas pedal to the floor and hold for five seconds.
3. Turn the key to the "off" position (don't remove the key), then release the gas pedal.
4. Wait at least two minutes for ECU to reset.
(you might have to do this more than once).