[Frazzydee]

Exactly, it seems that everyone else here is assuming the increased testosterone is because of increased perceived social status or, similarly, the result of a placebo effect causing people to "feel" more impressive/manly. This is a bald speculation without evidence.

Maybe the drivers DO feel more manly in a porsche because the drive is far different, which it is.

To draw a more accurate conclusion as to why, it may help to know how long after driving the increased testosterone levels lasted for.

If you really wanted to figure out why this occurs, a better study could involve a porsche fitted with a Toyota engine, and vice versa, to provide the same drive quality but equivalent external appearance.

Might also help to have a Porsche with a Toyota engine in a simulated environment where all other drivers are slower (so the Porsche driver is still relatively faster than other cars). Maybe the effect is from "dominating" other drivers.

TL;DR: Any speculation on why this occurs is pretty much baseless based on the information provided in the article.