Whenever the boost (psi) of a turbocharger or supercharger exceeds what the car has been set to.
"Dude, my car has boost Creeps right now, it spiked to 15psi and I have it set to 7."
When extra gas accumulates in your tail pipe and the heat ignites it causing a small explosion resulting in snaps, crackles, pops, and sometimes flames.
"Dude it's backfiring!
"mY sUpRa BaCkFiReS sO iT mAkEs 800 hOrSePoWeR."
Referring to a Limited Slip Differential; sometimes used to ask if the vehicle spins both wheels instead of one
"Yo bro, does it have a posi?"
"Can you do a posi?"