If your game crashes on load, you likely added an invalid part (e.g., putting a supercharger on an electric car). Reload your backup and edit more conservatively.
Some editors and save-game guides provide access to unique community wraps that are otherwise hard to find or share. Fixing Limitations: nfs heat save editor better
To manually manage or back up your progress, you can find your save files at these locations: If your game crashes on load, you likely