From the Super Mario Wiki
The Poltergust 4000 is one of Luigi's karts from Mario Kart DS. The kart's appearance resembles an upgraded model of the Poltergust 3000 from Luigi's Mansion. It has good speed, acceleration and handling but low weight, drift and items. Its speed is tied with that of the Gold Mantis. The pre-release version of the Poltergust 4000 had Professor E. Gadd's emblem on it.
The kart is unlocked for Yoshi and Waluigi as well when the player gets gold trophies in all Nitro or Retro Courses in 150cc, and becomes available for everyone else when gold trophies are obtained in every cup in Mirror Mode.
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