Hardcut limiter also know as POPCORN on diesel engines, its when the fuel injection  is cut off at a certain rev range and keeping the RPM sitting at that set rev usually around 3krmp and does not stop until the user releases their foot of the acceleration pedal.

This also makes the engine sound and reacted differently, causing a popcorn sound and visual effect via the exhaust gases at end of the exhaust pipe known as the "backbox"

though it makes no added performance gains to the engine it's more of a show piece.