I take it everyone is using the little spacebar 'boost' thing? It fires from the bottom of the bike so when you are leaning forward it boosts you along...
Also front flips are your friend
I seem to take a different route each time lol, at the end of the lap I use the last boost and one mid jump which clears the big bombhole thing and lands between the first and second rollers at the start of the lap. The hardest bit is timing when you fire the boost as you land so the bike doesn't snap in half
That 33 was a complete fluke, I can do 34's quite often but any faster will be complete luck!