i think after market computer are illegal the same way after market boost controllers are, bcoz u can adjust the emissions and horsepower of the vehicle. its a bit of a crock but im sure what they told terry is right.
anyway if they pull you over and go to look over your vehicle and you dont have the hand controller showing on the dash, they wont question you about aftermarket computer system etc will they, dont give them the reason to try, that is what i say.