Sorry, but you never knew the horsepower wasn't there in the first place, so doubt your gonna get it back. I had the same issue. In fact, even before I got this data, I found was commenting recently how strong the Santa Fe feels at 35Kmiles. The engine opened up real nice. In any event, here is a web-site that gives more details from the Hyundai president.
The best option to me is the extension on the bumber to bumper warranty since having those miles increased is probably the best return for me who will only keep the car for 5-6 years and be right around 100Kmiles then.