Hello. I'm an Ex-Mod. And I discovered this cheat about 2 weeks ago.
Basically you can Unlock the Top Fuel Dragster, F1, Nitto Stock Car, Funny Car and Mopar, ALL FOR FREE. And as many of them as you want.
I have en-scripted the nitto cheat below, enter your login/password and which car would like to unlock and submit it below. Once done, wait 2-3 minutes and close Nitto 1320 Challenge, and log back in under your normal login. Look in your garage and you will have whichever car you have selected. I'm not sure how long this cheat will be active so take an advantage while it still is!
In the Car Field, Put the car you wish to have unlocked. ( Remember Whichever car you choose, will go in your garage FREE )
F1 Type, Top Fuel Dragster, Funny Car, Nitto Stock Car, Mopar, Dodge Viper, Dodge SRT-4, Dodge Ram SRT-10, Honda Civic SI, Acura RSX, Lancer Evolution, Mustang Cobra, Mazda RX-8, Toyota Supra, Challenger RT, Charger RT, Nissan Skyline, AcuraNSX, Lancer Evolution, Subaru Impreza WRX STI