For this achievement, MAKE SURE you have 4 stars for the driving skill because you will need the jump upgrade for this achievement.
First thing to do is get the agency SUV in the garage. Now drive over to the Shai Gen district to where the boss Cowell is. Cowell is located straight ahead where Wang is. Second tallest building. If you haven't killed Cowell yet, just park your SUV next to the building and go kill him. Once hes dead, bring your SUV in and drive it into the elevator. Then grab your SUV and bring it up to the tallest floor. Now get into your SUV and drive it to the edge. Right when your at the edge, hold down B then while your in air, HOLD LEFT BUMPER UP and you should slightly make it to 2 flips by the time you are on the ground.
BOOM! Achievement is yours!