Gran Turismo 4 cheat codes have finally been discovered after nearly 20 years

But how were they even found in the first place?

Gran Turismo 4 Cheats: MORE DISCOVERIES

Experimenting with Cheats. (Gran Turismo 4 Online)

Gran Turismo 4 Cheat Codes Discovered Nearly 20 Years After

Gran Turismo (PlayStation Portable) - The Cutting Room Floor

In-game cheat codes have been discovered for Gran Turismo 4 almost

Gran Turismo 5 split open : PS1 & PS2 era tracks in game and

Gran Turismo 4' Cheat Codes Discovered 18 Years After Release

Gran Turismo 4 codes discovered nearly 20 years later - Xfire

Gran Turismo 4 Cheat Codes Discovered Nearly 20 Years After

Gran Turismo 7 Shows that Live Service Games Have a Long Way to Go