Revealing mistake: As KITT is rolling down the hill with the unconscious Michael inside, the shots of KITT from the outside show that the bonnet and roof have large and obvious gaps between them and the rest of the bodywork (presumably a stunt vehicle). When KITT fires it's turbo boost, the bodywork is its normal flush self again.

Knight Rider (1982)
1 revealing mistake in A Plush Ride - chronological order
Continuity mistake: Even after KITT's voice modulator changes to the three bars in the episode "Hearts of Stone," any shot of KITT starting himself up still shows the old voice modulator (a simple red square).
Michael Knight: I need ya buddy.
KITT: Right away Michael.
Trivia: Even though William Daniels provided the voice of "K.I.T.T.", he was uncredited throughout the whole series.
More questions & answers from Knight Rider
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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