Stuntman: Ignition

If you cant seem to get this in the Career. I found that the best level to do this in Quick Fix Freestyle, Level 4: Four Corners. it is very short and has about 6 or so 2-wheel ramps. One on each side of the road of the square block that you have to drive around. Plenty of opportunities.

To go on two wheels you need to make sure you are perfectly lined up to the small kicker ramp with your 2 wheels on your left or right side riding up it, throwing your car on to two wheels. Controlling once on two wheels is tricky but you can balance my moving the left stick.

I was able to get this achievement on a scene on the Never Kill Me Again movie in Career Mode. It was a scene where you get the opportunity to go on 2 wheels twice, the first opportunity comes quickly as you are about to enter the bridge. Do a long one there and again on the second change and you should have gotten 100 points.

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.