Pause and key in the following code: UP, UP, DOWN, DOWN, DOWN,
LEFT, RIGHT, LEFT, RIGHT, X, O. You should hear a noise and when you unpause you'll have max power (apart from the shield). It only needs to be done once in two player mode and you'll both be powered up. It works with the original Parodius aswell and you get a shield when you do it. What do you want more ? Should be no problem to complete the game !