Use the following trick to save the game while in God mode. Enable the God mode code, then finish a few levels with a three star rank or higher until you get a bonus level (Hard as Nails, Brawl, ect.). Then, play one of the bonus levels, die, and quit. This will reset the codes you enabled. Next, play any easy level and save at one of the check points. You will keep all the stars that you have earned with the cheat codes.