Go into the garage and press Y to enter walk mode. Go to the area where there is an arcade game next to some tool boxes and rims, to the right of the garage door. Press A to play the Geometry mini-game. To quit the game, press B, then A. Note: The arcade game is usually in the north area of the garage.
Win the the Kudos Challenge with a Steel medal to unlock the Delfino Feroce.
Win the Kudos Challenge on the Bronze setting to unlock the Ferrari 250 GTO.
Win the Kudos Challenge on the Gold setting to unlock the Mercedes CLK-GTR.
Win the Kudos Challenge on the Silver setting to unlock the Porsche 911 GT1.
Win the Kudos Challenge on the Platinum setting to unlock the TVR Cerbera Speed 12.
Win all of the expert (platinum) races in the Kudos World Championships. Additionally, perform the time attacks in circuit and car modes. Buy the cars with the Kudos that you have accumulated.
There seems to be a loop hole to get great combo bonuses. Unlike the original Project Gotham Racing, this game allows you to go through the cone gates twice. You can go through either forwards or backwards, and hence build up your combo bonuses.
When playing cone challenges, remember that it is all about the Kudos. If you look at the top ten ghosts of the Cone Challenge, you will see that people do not complete them fairly. They blatantly cheat by doing many, donuts, slides, and cone gates to accumulate the points. Even though this is not completely fair, it is also not that easy.
Notice that on all tracks there are skid marks (darker tarmac) before turns and fast bends. When you approach the darker tarmac, hit the brakes and make a concentrated, cleaner turn. This will ensure a faster time and less mistakes.
Note: This can only be done while playing on Xbox Live:
Step 1: While in an Xbox Live room choose the car that you want to have a new color. For example, the Porsche 911 GT1 is only available in one color (white). If you want to make it a different color, choose that as your car.
Step 2: You must now select the color that you want to change it to from another car in a different car class. For example, if you want the Porsche 911 GT1 to be pink, while still in the Xbox Live room choose the Classics car class, then the Mercedes 300SL Gullwing and select it in pink.
Step:3: Exit out of the Xbox Live room, but do not sign off Xbox Live. Then, back out all way to the single player mode, go to "Time Attack", then to "Car Challenge". Select the same car as you did the first time. For example, the Porsche 911 GT1. When you pick that car, you will be asked to choose a transmission type. Do not choose either of them; instead press Back until you reach the single player screen.
Step 4: Go into an Xbox Live room. You can either search for one, create one, or return to where you originally started by quick joining your buddies game. This glitch is probably most useful during games such as Cat and Mouse.
Note: You can only change it while you play online. If you go to change the car that you had just changed the color of, the color will get reset. You must take the color that you want from a different car class. This does not change the speed of your car.