So I finished the novel, and while it was a good read, there was no more Porsche. There was no real mention of his father's friend, and there was no more driving around in a Porsche. There was a car that ran out of gas, a few motorcycle rides into the sunset, but no Porsche. In the end I think the Porsche was more a symbol of money and maybe his father's true path in life, being gay instead of being married to a straight woman, than it was an actual Porsche. Sure it was mentioned a few times, but it was mentioned because that's how Craig, the main character, got to know the lifestyle he wanted. He did drugs, drank, and went to strip club when he was in the Porsche with his father's friend, and then he essentially becomes that lifestyle himself, sans gay relationships.
The Porsche helped him become himself, even if he had to get a little wayward before he straightened up and became a father. It was a nice read, but definitely not about cars. So if you're looking for a Porsche-centric novel, this one isn't it.