A missile and get out of the map. Actually, "out of the map" is a Halo term, but it works just as good here.
For the missile, get to the 4th checkpoint (doesn't matter which paths you take because there's always four at this point) and take the bottom ramp. At the end of the bottom ramp, bailout under the big metal ramp and you'll land on the ground with 2 signs. Wait and a missile will fall on you showing you you're going the wrong way.
To get out of the map, get to the last checkpoint - it's before the big fat ramp that launches you to the finish - and go backwards. It'll take some tries, but if you keep backflipping off every wall block, you'll make it to the bottom where it's barely considered in the track anymore.
This section is reserved for Confirmation/comments about this investigation. Investigations will remain open until advised by Redlynx that the final solution for each secret is found.