In the opening car chase, the vehicle being driven is a 4 door hardtop or 'sport sedan' meaning, when all 4 windows are rolled down, there are no posts/pillars between the doors. During the car chase, when they are coming upon the construction zone there is a 1 second glimpse of pillars between the doors. Then when they perform the stunt of driving on the two driver-side wheels, you get a clear view of the stunt car having pillars. This changes the vehicle from the '4 door hardtop' to a '4 door sedan', in effect, meaning its an entirely different variant of the vehicle being driven. The sedans are structurally stronger, hence why it may have been used for the stunt vehicle. It is stronger, cheaper, and easier to replace.
When Jesse, Tulip and Cassidy are pulled over and arrested, The Cowboy is shooting from quite the distance, presumably with a rifle. You can hear the shot well before the bullet hits, which in real life would be the opposite since the bullet travels faster than the speed of sound.
In the shootout at the beginning, Cassidy looks under the vehicle and it is high enough that not only is it sunny but a single skinny shadow stretches from one corner to another. Yet when he flips underneath the vehicle the ground underneath him is ten covered in shadow.