When you first access any of the Save or Load options inside any menu (Options > Memory Card, Factory > Garage, or during Story Mode), you'll see a message in japanese inside a blue text box, saying the memory card is being accessed. Without closing this message, hold R1+R2+L1+L2+Up+Triangle and press Circle. The message will change to another message, which is saying all ATs and parts have been unlocked. Pay careful attention: the blue text box must be onscreen. If you closed it, just exit the Save/Load option and re-enter it, this time taking care to not close the text box.