I don't know if anyone else has done this, but when you're on a race you can start with a boost i discovered it while racing against dark mario.
You just have to press Z, push the contol stick forward and when de countdown get's between 1 and Go press A (like doing a long jump) and you'll boost :3 It's kind of hard doing it but it works, i've done it several times.
You just have to press Z, push the contol stick forward and when de countdown get's between 1 and Go press A (like doing a long jump) and you'll boost :3 It's kind of hard doing it but it works, i've done it several times.