Invincibility:
Press L1, R2, R1, L2, Select, X, Circle at the title screen.

Finding Clues and Powerups:
When your on the road and are looking for clues or powerups, here are the best ways to get them. Go to a store called "Bookworms" which is located all over the city. This is probably one of the only stores you can break into but the lights have to be on. There are usually powerups and clues here.

Also, if you see a bad guy mugging someone, beat him up and you'll usually get a clue. Next, if you come across a brown door on any building, break into it and you'll find a little energy. But if there are alarms going off in front of the door, a clue will be inside. Last, if you see four mini fences surrounding a box, just drive over it and you'll get TWO clues.

Super Health:
When you are driving around the city, and you spot a yellow motorcycle follow it for awhile and you will get a super health.