(Spoiler below) After fooling around with Codebreaker v.9, I now have a clean gamesave (if anyone want it, I can email it to you):
All gold licenses
All arcade tracks unlocked
Most cars from garage selectable in arcade also
Special black version Toyota GT One Race Car
Special black version Mazda 787B
Special black version Nissan R390 Race Car
Special black version Nissan R92CP Race Car
Special black version Polyphony Formula Gran Turismo 04 (the 100% prize)
Polyphony Formula Gran Turismo 04 (purple/white)
Polyphony Formula Gran Turismo 04 (blue/white)
Polyphony Formula Gran Turismo 04 (red/green/white)
Polyphony Formula Gran Turismo 04 (white)
Polyphony Formula Gran Turismo 04 (black/silver)
Polyphony Formula Gran Turismo 04 (yellow/black)
Polyphony Formula Gran Turismo 04 (orange)
Polyphony Formula Gran Turismo 04 (red)
Polyphony Formula Gran Turismo 04 (green/yellow)
Polyphony Formula Gran Turismo 04 (blue)
Mercedes Sauber C 9 Race Car '89
Jay Leno Tank Car '03
Secret Prize cars (~15) you can't buy or see at the dealerships (e.g. Mitsubishi
FTO Super Touring Car '97)
Other handpicked cars that I like (~60)
Money: $1,000,000,000
A-spec points: 0
B-spec points: 0
Percentage completed: 0%
Days: 250
This is my starting save point. I am now going to start the game and race manually and without any more cheats.