I have figured out a way (by luck) to make formula 7 invincible. (only works on stage 5 though) when ur on stage 5, when u start, go left. u will see lots of bridge things. go to them and face the inside of one. drive the car backwards and forwards, smashing the back and front till the spoiler is broken. then, u will be invincible. go smash EL King without losing any life! whatever u do, when ur invincible, dont go through the electric hoop (repair hoop), or you will no be invincible anymore.
hope i helped :D