Choro Q Coins are scattered throughout the world for you to find. Some are in really easy places and some you need to have certain parts for your car in order to reach them. Once moved there is a inhabitant in My City called Coine, who will give you special parts/bodies for collecting so many coins. Check out Stamp 46 for the list of prizes.
Another useful thing to have obtained prior to looking for all the coins would be the Coin Radar, obtainable from Keitel in White Mountain, Instructions Here.