http://www.gamewinners.com/playstation2/GranTurismo4.htm

http://www.cheatscodesguides.com/playstation-2-cheats/gran-turismo-4/

http://cheats.ign.com/ob2/068/489/489327.html

http://www.cheathappens.com/cheat_index.asp?titleID=10161

http://www.cheatscodesworld.com/playstation-2-games/gran-turismo-4-cheat-367.html

http://www.supercheats.com/playstation/granturismo2cheats.htm

http://www.supercheats.com/playstation2/granturismo4cheatcodes.htm

http://www.gamewinners.com/playstation/GranTurismo.htm

http://vgstrategies.about.com/od/ps2cheatscodesg/a/gt3aspeccheats.htm

http://www.thegamingonline.com/Playstation/Codes/gran_turismo2.htm

http://www.gamerevolution.com/cheat/ps2/gran_turismo_4

http://www.cheatcc.com/psx/codes/gt2.html