Polyphony Digital is engaged in an arms race. With every major update (Spec II, etc.), they attempt to obfuscate save data. Furthermore, Sony is pushing hard for cloud-only saves.
: Use scripts on a PC via PS Remote Play to automate races like Paname, which can earn over 16 million credits in 24 hours without manual save editing. Official Methods : You can earn up to 2 million credits save wizard gran turismo 7
While is a popular third-party tool for modifying save data on PlayStation 4, its effectiveness for Gran Turismo 7 Polyphony Digital is engaged in an arms race
Using editors to gain unfair advantage in online multiplayer is unethical and increases risk of penalties; prefer using them for single-player experimentation. : Use scripts on a PC via PS
: You will earn many cars naturally through licenses and missions; save your credits for high-end "Legend Cars" or essential tuning.