This is a very tricky achievement well worth all 30 gamerscore points you'll receive for it. For this acheivement you'll have to get a Gold Medal time on all 30 levels in the game (up through 5-6.) The only advice I can give you here is to use the YouTube videos in the Speed Run thread right here and practice, practice, practice. The videos should definitely help on a lot of the levels to find a lot of shortcuts as well as "Hidden Paths" so that this goal is attainable. Credit for videos go to the people that put them up on YouTube. Good luck!