Essentially all these stories are apocryphal. Even this vapor lock story.
Sorry but even before today, having a automotive engineer sent to a random person's home over what clearly sounds like a quack letter seems implausible to me. The dictates of capitalism, human resources, and the politics of the workplace would make this difficult if not impossible. Even in the past when there was more human capital in support positions and more of a sense of customer service.
Way, way too many suspicious stories involve high-level people being involved in trivial issues. I just find it all pretty suspicious. Real stories tend to start with poor customer service at the dealership and being mocked by managers and mechanics. Not some unrealistic ideal white knight manager sending off engineers to people's homes. Imagine how many weird letters a place like pontiac gets. They don't have the manpower to do this if they actually chose to do it, and engineers might balk at the idea of doing at-home support too.
Pretty much any "idealized Americana" business story should set off BS alarms in us. "Oh a trivial problem with your car? No problem ma'am, I'm sending our top engineers over tomorrow," doesn't happen because its costly and unsustainable. Instead ask anyone who has odd car problems. Its endless painful calls and visits to dealerships and mechanics. There's a reason we have lemon laws for cars. Its because whats described in this story doesn't actually happen and people demand restitution.
I don't doubt that someone had a famous vapor lock shopping story (ive heard different versions of this story, usually about a housewife picking up her child from a nearby elementary school), but over the years these stories get modified into memetic structures based on dishonesty because most people are social capital seeking and having a humorous story provides them the immature ego boost they need. So "wow my car had vapor lock when I make quick trips" became "So the CEO of Ford came to my house to look at my ice cream car..." The latter is just more interesting in the market of storytelling.
That is to say, the ONLY reason this story is here is because its been modified to be memeticly attractive. A "boring" (i find old technology faults interesting, personally), but a "boring" story about vapor lock wouldn't make it to places like HN or reddit, which are memetic responders (upvote/downvote mechanisms) and lowest-common denominator (by this demographic) popularity machines. But dress up that boring story and now everyone is repeating it, often times claiming its their story and they know the people in it! The same way the comment you're responding to probably doesn't actually know the famous "unplug the server at 5pm" person.