This may come as a surprise to you, but there's a little bit of racing in this book.
We know. We had no idea, either.
There's literal racing—Denny drives racecars for a living—and then there are moments when racing is used as a metaphor to describe the way Denny is handling a situation. This is most apparent when Enzo pulls back in his narration to describe the racer as a creature in the abstract, or when he's applying a saying that Denny has taught him about racing to Denny's own life.
In fact, the most prevalent and important quote of the book—"Your car goes where your eyes go" (14.1)—is basically a dual metaphor for the novel as a whole. In racing, when you're steering a car, your car literally goes where your eyes take it, since when driving as a responsible driver you are maintaining the speed, velocity, and direction of the vehicle. It's the movements of your body, which are directly related to the movements of your consciousness, that steer the car.
Look at that: we're not just a study guide—we're a driving guide. too.
It's the same with life, where you're driving your own metaphorical car. You are in charge of the paths you take, and your car is likely to follow where you set your sights, or your goals.
No wonder racing is such a great metaphor for life.