Hi Amanda
Have a look at the Sorento Forum
http://kiasorento.proboards46.com/
I used to have a Powerbox fitted, not the same as a remap, and either it or the Supermarket fuel I was using caused the exhaust gas recirculation valve and turbo intercooler pipes to gum up.
Yours is the same year as mine , probably high mileage. Do you really want to try and extract more power? There's always a cost and if not fuel burn then certainly I'd suggest more strain on the transmission etc. I tow a heavy TA and in fairness have never felt embarrassed by a lack of power. In fact the torque on the Sorrie is extremely good.
Before you spend any money on remaps it may be worthwhile having a diagnostic check done by you local Kia dealer to establish the engine's general health, eg compression ration injector function , turbo pressures etc.
Steve In Leo on here has done some very successful remaps and may be able to give you a good steer.