Hullo ferociter,
I think I found a bug. I found it in bouncy maze, but it might apply to all forced speed areas.
Basically, in the bouncy maze if you turn around, come out the way you came, but hold brake, then reverse, you can remove the forced speed, whilst remaining in the maze.
IDK how to attach a video, but basically if you enter the maze from the top, bounce straight back out holding brake, then reverse you can get into the maze without the forced speed.
I assume this is because you never leave and re-enter the forced speed gate, so the game doesn't apply the effect.
IDK how to attach a video, but try it.