not sure about ri, but you should check if they have a referral program like ma. in ma if the pid values of your pcm arent the same as last years inspection it can fail you and refers you to a state ran inspection site to investigate (thinking you used another car for the test). if they dont have a program like that the obd test most likely just checks readiness status and cel state and if no codes and readiness is complete you're good. i dont think its a viloation to have another cars computer, people buy used computers all the time. in ma engine swaps are legal if you use the emissions equipment, it tests for the year of the engine instead of the car, but the swap has to use newer engine on older car, not vice versa.