Don't know if it is a glitch or smthg like that but it worked for me, i now have the full outfit from the Yeti's missions, here's what i did:
1. Race against the Yeti on any track.
2. Beat him.
3. Turn the wheel, DO NOT GO BACK TO THE WORLD MAP, directly go to leaderboards, find the crapiest racer into it and fight his ghost.
4. Beat him on all the checkpoints and you'll still win the furs.
5. Repeat.
It costs you only 5 fuel, and it's pretty fast!


