I was over on the Bronco forum and apparently throttle cables get slack (Who knew?) Have any of you guys checked and found slack in your cable? Seems the Bronco guys are using zip ties to take up the slack where the cable meets the pedal.
Get a friend to push the pedal to the floor and check that the throttle is fully open.
Get a friend to push the pedal to the floor and check that the throttle is fully open.