In GM K2-generation pickup trucks, there is such a thing as upfitting. It's basically adding an OEM switch (soft switch) and an OEM relay placed in certain port in the fuse box. The switch controls the relay through the canbus. This requires a good knowledge of the canbus structure. I wonder if that's roughly what KIA AUS did.
Does the OEM bi-modal exhaust come with a nifty OEM-looking switch?