When Ponch drives his Firefbird on two wheels the car is clearly outfitted with special wheels and tires to facilitate the stunt. In other scenes it has it's normal chrome mag wheels.
When Ponch is driving his personal car on two wheels, a black safety strap is visible hanging out of the driver's-side window.
During the final chase in the gravel pit, when the thieves car crashes there is a dummy dressed as a person in the backseat.
When Ponch performs the pipe jump in the gravel pit, there is a ramp inside the pipe. Even if there's an explanation for a pipe that large in the middle of a gravel pit, there's no plausible explanation for a ramp.
In the last scene where the three criminals are being pursued into the gravel pit ,you can see that the criminal driving the getaway car is wearing a cowboy hat and the other two passengers are mannequins. Also when they crash onto the back of the flatbed truck the driver is wearing a helmet now instead of the cowboy hat.
In the scene where the the bus robbers take off in a car , Ponch & Jon are flagged down by the passengers & ride off in the direction of the fleeing bandits and come upon a car accident. At the accident scene , you see a guy (wearing a blue denim jacket ) who apparently wandered into the scene and is waved on by a seemingly frustrated film crew member.
In opening scene, Jon admonishes Ray Conner for the way he drove into the CHP parking area, although Conner was already parked within the facility when he approached Bonnie.
In the last bus scene where Ponch & Jon are pursuing the stolen bus on the highway in Ponch's personal car, the ramp that causes Ponch's car up on two wheels is visible.
Once Ponch and Jon are in pursuit of a hijacked tour bus in Ponch's personal car, it is unclear why Jeb allows the bus to get away. Jeb seems more concerned with congratulating Ponch on driving his car on two wheels than on pursuing a bus with more than a dozen hostages aboard.