First off, the phrases "PAL GT3" and "Gameshark 2" don't go together. If U have the PAL version of GT3, U need an AR2, not a GS2. It is also my understanding that GS2s will soon be of the market, and AR2 will be making the device for both PAL and NTSC.
At any rate, if U have the correct cheat device:
If U haven't already,
read This Guide .
A few important things to remember are,
1- never save your game until U have checked the car in the garage!
2- U can only use body and color codes together that normally occur in the game. Example: U can't use a color code from a speed12 on an RX8, the color codes are specific to each body.
3- U will notice that those links discuss the codes as being GS2/Codebreaker codes. That was true when this all began. Since then Pelican has released Codebreaker V4, which can not use those or any GS2 codes, so the must be converted to CB format. This can be done, with some work, but has never been requested.
Check it out
HERE for some codes, and other help.
And this is
The Parts Department , which is part codes only.
And U might want to read
This Thread in general.