Stuntman: Ignition

If you have not unlocked this simply by doing the campaign i could recommend doing this on the mission "unsung hero" on the strike force omega levels. there is a 180 turn half way through the level and its an easy level taking around 1 minute. i can confirm you must finish the level to get the achievment, not sure about failing it.. but you wont any way. also this map is good for the 20 over taking achievment duster!!! there are 3 opportunities for this. good luck

To do a 180 degree stunt you need to be going at a fast speed and then slam the left stick left or right whilst holding the B button to spin your car around so it's facing the other way.

As you need to do 30 of these you may not get it through your first playthrough however if you don't you can simply do one of the many scenes which include the 180 degree stunt (lots do). I found that the Quick Fix event is good to grind this on as they are quick and end with you needing to do a 180 degree stunt.

To get the achievement you need to make sure you get to the end of run for it to count. It also may be possible to get it by purposely failing the level afterwards but I can not confirm this.