Boston is like a forced induction engine. Naturally aspirated engines just suck in air, while forced induction engines have some sort of device (a turbocharger or supercharger) that powers a fan to blow compressed air into the intake, which does...things. I know nothing about cars.
One thing I like about "Peace of Mind" is that, like most Boston songs, it's built layer-by-layer: rhythm guitar, then drums and lead guitar, then vocals, then harmonies.
The harmonies are the second-best thing about "Peace of Mind" because that's when you really get the compressed-air feeling. Everything's just thick and high-pitched and in your face, like sticking your head out the car window.
The best thing about "Peace of Mind" is the switch from C# minor in the intro to E major in the verses back to the C# minor in the chorus. The verse is such a cruisin' Edgar Winterish adventure that you forget that most of the song's in a minor key by the time you get back to the chorus, at which point it feels like a tweak. It's shocking, but not unpleasant and frankly, a little titillating, like a dash of citrus or a bit of light BDSM.
All great Boston songs are like this, to a certain extent--getting your nipples tweaked while someone blows compressed air up your nose and pumps bitchin' guitar solos into your ear.