Get a Viper GTS fully tuned and go to the oval track. Drive about 210 mph. When you are about to turn, turn the other way into the wall. Hit the nitrous and hold it while still turning into the wall. If done correctly, your car should go up and fly. You must be in the dirt part of the turn. Try using the nitrous two seconds before hitting the wall and hit the wall (wire fence) at about a 30 degree angle.