It’s supposed to be a V8, but sounds like a V6 in-game. My guess is that this sound was supposed to be applied to the Hoonitruck, but they applied it to the Silverado instead by accident.
Or they dont have the file lol…
It’s BMW straight-six, not the Hoonitruck. Jonk acknowledged it in the main car sounds thread and stated it will be fixed in the Fortune Island update on the 13th.