Levels UpgradedG 35

Levels Upgraded G35:
Upgrade 100 stages

Basically the achievement is for upgrading anything on your cars 100 time. You can upgrade everything out to level 5 with a one star car 5 times which is what I did to make it go faster. You can level up your cars by selecting the car you want to level up & then spending your coins to level it up. When it is level 5 for all upgrades then upgrade a new one. You will most likely get this by naturally progressing through the game, unless you are at the last few, then you might do some upgrades just because you want this achievement.