remapping the ECU is a way to get more power out of the engine, it is great for diesels.
1. It will void your warranty.
2. In the long run the engine will be less reliable.
A better solution is to put an add-on between the ECU and the diesel pump, so when you go to service you just have to remove it.
You don't have to look far:
In anyway, don't understand that I recommend putting one, I do not.
I didn't put one and I am not going too, I find the Sorento GREAT as is.
I did see it work on a Mitsubishi Magnum, more power for sure, but much more smoke as well.