There are a number of things never specifically stated in the movie:
- What is the Racer(Wraith) exactly?
- If he is someone come back from the dead, where did the futuristic car come from? Obviously he is Jamie come back from the dead, but the question still stands.
- What is the purpose of the suit that he wears.
This last weighs in on the items that disappear after each fatal crash. I always took the post-crash sequence to actually just be all of the parts of the Car and the Racer reconstituting. They show specific items disappearing to relate that the opponents car parts are left on the road, their car seemingly being destroyed without the help of the Wraith car to anyone that does not see the crash.
Note also that the Racer wears a black body suit that has a number of hoses and tubes running over it (but no leg or arm braces). Those items that we see disappearing after each race just go to show the viewer that the Car is not leaving any of itself behind. With a limited budget, I can imagine they were unable to have large portions of the car disappearing.
After a little more thought (and watching key parts of the film again) I also kind of wondered more about the suit. At the end of the film, the suit clad figure gets out of the car and then turns into Jake. He doesn't take it off really, so much as transforms from suit to human.
It seems that the suit clad figure is not human. Perhaps the items we see disappearing are not only parts of the suit but are additionally parts of whatever the suit contains? Unfortunately there is little that the movie tells us about this also.
A Science Fiction fueled beyond-death revenge story. That's what it is.