Continuity did't exist back then. What episode had the most errors

A lot of stock footage from other movies was used too. I'll never forget the episode where KARR supposedly explodes after going over a cliff, but the exploding car is clearly a car from the 60's or 70's and no where near the make and model Trans Am used for KITT and KARR.

When theres no more room in Hollywood, remakes shall walk the Earth.

What exactly is your criteria, storyline or just stock footages? Because their was continuity as far as storyline..

The simple fact that KITT always changes from being a invincible car that protects Michael to being a helpless Baby.
In the Pilot it gets explained that KITT's main directive is to protect the life of Michael Knight, so when he drives up to the Van, KITT simply takes over and steers around the Van.
In the episode Blind Spot on the other hand, when he and David are trapped in the Car Compactor he says he can't do anything and Michael has to press the Turbo Boost Button.
Same in the episode "A Plush Ride" where he has to first wake up Michael so he can press the Turbo Boost and the Turbo Boost suddenly doesn't make KITT jump but just blows out some smoke which somehow stops the Car.

One thing they changed was Michael Knight's Face being created to resemble Wilton Knight as a young man, that was explained in the Pilot. In the first Goliath episode that was retconned to Michael Knight's Face being modelled after Garthe.

Also the Buttons (where the Turbo Boost and all that is) change their functions (and their names) from episode to episode and sometimes in one episode even, like in "Just my Bill":
http://www.regelt.org/knightrider/bilders/sprittforfun/kr106_3322.jpg
http://www.regelt.org/knightrider/bilders/sprittforfun/kr106_3701.jpg