Plot hole: How could the police miss finding Cybil in the trunk of Michael Zane's car when it was in an impound lot? They would have definitely searched the car if he was found in violation of a federal offence (for carrying the weapons). Even if they didn't do a search, they would certainly have heard the sounds that Cybil would have made from being locked in the trunk.
Factual error: Although you'd have to actually live in Boise to catch the myriad of differences from the movie town, the most glaring is that the movie Boise appears to be a lush rainforest, like Vancouver or Seattle. The real Boise is strictly desert, and you won't find those green interstate medians anywhere near here.
Visible crew/equipment: When Mike, and Cybil are talking in the parking lot and Mike is about to get into a Cab, after Mike says "I don't even know who I'm talking to anymore"; you can see a crew member in the background telling a spectator to move out of the shot, and the next shot also shows a lady looking into the camera in the background.
Continuity mistake: During the scene where the kid and his mom are being chased by the Wombat truck, they show them both wearing their seat belts. When the car is struck and goes up on its side, the kid slides all the way over into his Mom, he's not wearing his belt, but when we see the car again on all four wheels the kid is again wearing his safety belt.
Factual error: While tracking Kevin Costner, Thomas Hayden Church reads a bio listing Costner's birthdate as Jan. 8, 1955. He then says Costner served as a medic in Vietnam. But Costner's character would've been too young for Vietnam. He would've only become eligible for military service at age 18, in Jan. 1973! That was the same month the U.S. ended the draft and began bringing home the troops. Even if he volunteered, it still would've been too late to serve in Vietnam.
Plot hole: Murphy and Michael are in jail together, Murphy calls Jack to get him bailed out and tells him that he is using a fake name and he needs to make bail before his prints come back. All telephone conversations from jail are monitored, also, when a prisoner is released from a cell to make a phone call he is cuffed and a deputy is standing with him listening in.