(at around 17 mins) Michael (David Hasselhoff) is driving with a woman. When the shot switches to a longer shot, not only does Michael - who's impersonating Garthe with a small beard and mustache in the closer shot - lose both aspects of that facial hair, but it's obvious that the driver and passenger are both different people. When the shot switches back to the closer shot again, it's the original people again.
The shot of KITT on his side has a flat hood, missing the raised scoop.
K.I.T.T.'s infrared scanner is somehow able to see through a lead door. Even if an infrared scanner could see through a lead door - which it couldn't - it would not show the scanned objects in full color.
When Michael is driving to Ceasar's palace, his script is visibly lying on the passenger seat.
After KITT collides with Goliath, KITT's undercarriage is completely flat with no drivetrain or other components, showing that a completely empty shell was used for the wreck.
The rocket launchers on Goliath are loaded before they are even bolted on to Goliath.