Revealing mistake: When KITT is in the valet carpark, he pushes the cars in front of him forwards. It is very obvious they have attached rubber protectors to the bumpers to prevent damage. Also, when KITT is driving by himself 10 seconds later, you can see the stunt man's hands driving the car.
Revealing mistake: Watch the scene where Michael fights two guys for a purse. Michael calls KITT for help. When KITT jumps off a cliff, an old vehicle is the one that jumps off the cliff instead.
Answer: I would say that unless there's visual evidence it was another K.I.T.T. car, as in you could see the bar scanner or cut steering wheel, people on here would correct the mistake by saying more than one 1982 Pontiac Firebird Trans-Am was sold and there's no reason it's meant to be a random car.
Bishop73