Take the downloaded .sav file (often named NFS11Save_100.sav or similar) and place it into the save folder. Rename it exactly to what the game expects, usually SaveData.sav .
In some cases, a 100% save can help bypass issues where Limited Edition cars (like the Dr Pepper Camaro) are no longer unlocked by the (now broken) EA servers. Guide :: 100% save game file UPD!!! - Steam Community need for speed shift 2 unleashed save game 100