I believe the accelerator position sensor is adjustable as well as perhaps the throttle position sensor, but if these were far enough out of adjustment to cause an issue, your check engine lamp should be on. I've experienced defective sensors, but never one out of adjustment on this electronic throttle system (XG, Santa Fe).
You could try reinitializing the throttle plate, but I suspect your dealer has already done that. To reinitialize, turn the ignition key to the on position (do not start engine) and immediately turn it back to off. Then leave the key off for at least ten seconds. This often relieves some of the suddenness of the acceleration.
I still think, however, that if the throttle is binding, that's an issue. I don't think it'll significantly affect your fuel mileage, but it's a serious safety concern. Of course, I haven't driven your vehicle, so I don't know how much it sticks.