Awarded for completing the quest in T-Bone Junction entitled "Greasemonkey." You get this quest from Scooter as soon as you complete the DLC's second quest, "Boost the Monster." That quest requires you to find three parts for the new vehicle.
The supercharger can be found in the lowest portion of the level closest to the far right semicircle as seen on the map. It's almost dead center of the map and behind a small shack.
The nitrous oxide tank can be found in the middle of the right semicircle of the map in a trash pile Near Marcus' place.
The exhaust pipe can be found at the bottom of top left semicircle attached to a car that's crashed into a pole. It's right next to Zed's place.
With all three parts in hand, return to Scooter's and put the pieces on the Monster. After installing the parts, hit the switch and watch the scene. Once the Monster disappears, turn the quest into Scooter for the achievement.