This seems to be giving a lot of people a hard time. For this you have to hit every stunt hoop in one race. Do Level 9 as it only has 5 hoops and its easier than the other Race levels. Just take it slow and get used to the Level first. When you are getting near a ramp, tap the to get some boost going, then press to jump off the ramp, then either press the :ybuy:, , or to do the correct trick. The buttons appear in random order and they change when you restart or fail.
Note: Press the correct button before you go through the stunt hoop. Achievement unlocks once you go through the finally hoop, so you don't need to finish the race.