Check out Joystick Mapper from the Mac App store (about $6). I bought a PS4 dual shock controller last week and have mapped the controls on it - works fine with Grid. I have mine plugged in via USB, I don't think the wireless works. This kid https://www.youtube.com/watch?v=h4PtEUWyNzI has put a tutorial on YouTube so you can learn how to use Joystick Mapper (it's not obvious when you load it up). I screen grabbed the controls for the game, then just selected each control, pressed scan, then pressed the game pad control. Don't forget to select your setting once you have completed it (oversized check box). Good luck :-)
