You are a "warrantee" and Kia is a "warrantor", because Kia has provided you with a "warranty".
Now that I've got that off my chest, to answer your post:
I don't think anybody can tell you for certain what such a change would affect, but if the car has been modified I feel you'd be inviting trouble. It could be argued that the paint warranty should remain valid as it's unrelated, but who knows how Kia would approach that. If you were found to have modified mapping I suspect Kia would drop any engine or drivetrain warranty claim like a hot potato.
You also have to let your insurers know. If you had an accident and it was found you had remapped the engine without telling them they would drop you like a ton of bricks just covering the third party damage if any.