When you're doing Stunt Rider, speed and tricks aren't always the best option. Sometimes it's best to brake and forget tricks, progress is a ton more useful.
Bandito Chinchilla is pretty advanced. When you have to fight a new enemy, the HP doesn't change alot, but the 1st boss is like 2 minor enemys you 4th encounter. Beware of the froggie enemys though!
Sumo Saucer is as bad as a tongue twister. Much too hard to explain.