This is done on the right side of the map. There is a double loop and above that a single loop. It is done from the single loop. Go all the way around it and straight on keeping to the right. When the road goes downhill there will be a lot of steps in front of you to jump from. Fast bike/car needed with Nitros. This can be done in race editor which will allow you to drive without cops or traffic. Refer to "Waldo's Still Missing" achievement for details on using race editor. 20 seconds into the video this is shown.