If you haven't already been using them, try finding the almost-transparent chutes that run up above the racetrack. I used them almost all the way (granted I had an Xbox controller) and found it pretty easy. Take it slow at least once to work out a route.
There's also a shortcut near the end, on the right side of the track a purple tunnel opens up just before an accelerator archway. There are censors in there, though, so I don't know if it will help you much. It's possible to just avoid them but might be tricky with the keyboard.