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.