If you watch the video, you can make up 4 seconds going about it a bit different. when you go through CP no3 (by tiny tina's) turn right and boost onto the ramp. IF you can make it onto the bridge steer to the left center before the road ends, you should land to the left of the large sign and a straight shot to the last CP. Use whatever boost you have to the finish line.
Also big tip - IF you're using boost and go airborne, turn the boost off untill you land. Alot of player will run boost dry even if they're in air... since you can't boost after a jump, you're just wasting it.