I'm finding out that these are what's known as "Single-Event injection tunes." Lots of stuff to read about when you know what words to look for.

Supposedly there are some gains to be had by pilot injection other than just reducing noise. It pre-heats the cylinder and helps the primary injection burn a bit better. Maybe I'll tinker with it after I get that sweet 12V sound.

Notice how nobody wants that lovely 24V sound that the VP44 trucks made? Hmmm. I actually kinda liked it. Ain't nothin' louder. I wonder what it would take?