You want help? Sure. Here's a solution: drop the GameShark. GT4 is challenging, but not impossible. What's wrong with a little hard work in GT4 without the GameShark? So if you want some GameShark codes, here's one:
DROP THE GAMESHARK AND PLAY GT4 WITHOUT THE GAMESHARK
This will grant you 100% Completion, win every race, all 80 Gold Prizes, the Forumla One race car, and online play. Here's one more code you can use:
YOU DIG PLAYER?