On one occasion during the car chase when the Monte Carlo runs a red light/stop sign and barrels through the intersection, a nearby gray pickup truck swerves and stops abruptly, causing a large squarish cardboard box to fall out of its loaded bed and land in the roadway next to it. But when K.I.T.T. follows the Monte Carlo through the intersection, the gray pickup's bed is empty of visible cargo, and there is no box sitting beside it.
At the formal party scene near the end of the movie, Nina is giving Michael a sour-faced grilling, yet in the very next shot that shows Michael walking away, Nina is smiling broadly - even in side-view, you can clearly see her white teeth.
When we first see the villain's car, it is definitely a blue color. But in subsequent shots of the Monte Carlo during the chase scene, it is a dark color, like black or deep gray/brown.
When KITT tells Michael that the bad guy they're chasing has stopped at 997 Grandby street, Michaels says "That's where Rachaels boyfriend lives." In the next shot as KITT turns right, the shadow of the camera and the operator panning it to follow KITT can be seen on the street.
At initial showing of Mexico, footage alternates back and forth between shots in Mexico, and shots in East LA (perhaps Figueroa near Avenue 26) showing Kitt Driving.