When the Exterminator sets fire to the gang members doused in gasoline, the flamethrower is a thin little blowtorch, then in the next scene, he's back to using the big bulky flamethrower he's been using throughout the film.
The shape of X's hair repeatedly changes throughout the movie.
The news anchor at the beginning says The Exterminator got his name by the media, but in the first film it is Eastland himself who comes up with the name when signing a letter to the police.
In the scene where X summersaults of the roof of the armored car he clearly jumps onto a blue madras and not the asphalt (visible in the 4:3 VHS release).
After the Exterminator sets fire to the gang caught in his gasoline trap, he's about to remove his welders mask before it quickly cuts to the next scene.
When John is talking to the bartender near the start of the film, the camera, camera operator and assistant are reflected off the mirror in the background.
When X gets blown off the catwalk, you can see the safety goggles that he's wearing.