Gran Turismo 3 Cheats

I dont mean to waste time but here is a cheat hardly worth using.
In arcade mode go to hard difficulty but dont click on it.
Instead hold L1 and R1 (or it could be L2 ans R2...I'm not sure so try both options) and then the hard difficulty should change to proffesional.....
It's the biggest waste of a cheat ever but if you want to make things harder on yourself try it!!! d:>

You need to have two PS2 Memory Cards for this to work. Sell all the cars you've won/acquired except the one you want to modify in the Slot 1 game but save the game afterwards to Slot 2. Use the cash from the sale to ramp up your car and save the game to Slot 2 again.

Now load the game in Slot 1 (the game that still has all your cars) and ask to trade with Slot 2. Once you finalise the trade, you can save the game to Slot 1 and copy the Slot 1 GT3 game block to Slot 2 and repeat the process.

To unlock cars do the following:

This isn't a cheat so much as an effective strategy for beginners. First get a car to the 300 hp range, then race the Super Speedway track in the Beginner class GT World tournament. If you race against only Rally cars, you should be able to win, for $10,000 a win. Do this about 10 or 15 times, until you have enough to get a good car and tune it into the 500 hp (or higher) range. From there, enter the European Championship series in the Amatuer class. Win the first four races, then save your game. Enter the fifth race and immediately exit. You'll win the series and win one of four bonus cars. If you get a car other than the Vertigo race car, exit out and load your game to quit the fifth race again. Do this until you get the Vertigo race car, which you can sell for $300,000. You also should win about $50,000 from the four races and the series win. This should take about 20-25 minutes, and yield around $350,000.