Here is the full list of all 12 New Rally-X achievements worth 200 gamerscore. It takes around 1-2 hours to unlock all of the achievements on Xbox 360.
Collect a Lucky Flag with more than half fuel remaining.
Collect the Lucky Flag.
Collect the Special Flag before collecting another flag and finish the stage without losing a life!
Collect the Special Flag before collecting any other flag!
Collect the Special Flag.
Score 20000 points and gain an extra life!
Clear Round 4!
Clear Round 8!
Clear Round 12!
Clear Round 16!
Clear the first 7 rounds without losing a life!
Score 100000 points and gain a second extra life!