You have to get twenty turbo boosts on a single lap, which you get by drifting for certain periods of time then letting go of . As you drift, the controller will vibrate when you get your first boost, then vibrate twice more to indicate level 2 and 3 boosts. These level 2 and 3 boosts only count as one, so you should boost as soon as it vibrates once. This way you can quickly boost then start drifting again on the same corner, getting you two or maybe three boosts on a single turn. The best track for this is the Lava Lair track, since it’s one of the longest in the game and you’ve got plenty of opportunities for boosts. CNash also suggests the Treetops course, using Shadow.