Revealing mistake: The "blower" on the yellow Firebird never runs. NO wonder he couldn't beat the Wraith. (00:44:10)
Revealing mistake: After Packard's car crashes with the Turbo Interceptor, his body is lying on the mangled car. If you look close enough you can see Packard's head moving slightly as if trying to hold still.
Revealing mistake: As the sheriff's car broadsides the car carrier, after the explosions, you can see the cars were junkers, set up to fall off the carrier.
Chosen answer: I believe they are markers to show how many people are left to take revenge on for his death.
EMTurbo
The problem with that answer is that the Wraith had to kill five people (Oggie, Minty, Skank, Gutterboy and Packard) and he only had four of those metal braces. If he had one for each gang member he wanted revenge on, he would have had five. I think he was only given four chances to crash his car and reassemble, and once they were gone, that was it. That's why he killed Skank and Gutterboy at the same time.