Unlock mojose car, tokyo highway, austen powers car and anakins pod racer:

 At the tittle screen enter RIGHT,  LEFT, RIGHT 2x, UP, DOWN, LEFT,
 DOWN, UP, each time you want to geat one of the cars, next go to options
 password and enter the following codes:
 For mojo car enter: mojosmash
 For the tokyo highway enter: tokyowaya
 For austen powers car enter: haybaby!?!
 For anakins pod racer enter: theforce!a.

 Submitted by: the dark one
 

 Cheat mode
 Enter "Nosliw" as a name (case-sensitive) to unlock all cars and tracks.  
 
 Faster Mercedes
 Enter "Reki" as a name (case-sensitive). 
 
 360 Spider and 360 Modena - Win the Kudos Challenge level 9.
 911 GT2 - Win the Kudos Challenge level 12.
 Aston Marton V12 Vanquish - Win Arcade Race level four.
 Boxster S - Win the Kudos Challenge level 2.
 Camaro SS - Win all golds in Quick Race level two.
 Carrera GT - Get 150,000 kudos.
 Corvette ZO6 - Win the Kudos Challenge level 7.
 Delfino Feroce - Get 75,000 kudos.
 F355 Spider and 355F1 - Win all golds in Quick Race level four.
 Ferrari F50 - Get 200,000 kudos.
 Focus Cosworth - Win the Kudos Challenge level 3.
 Lancer Evolution VII - Win all golds in Quick Race level three.
 Lotus Exige - Get 50,000 kudos.
 Opel Speedster - Win Arcade Race level two.
 Panoz Esperante - Get 25,000 kudos.
 RX-8 - Win Arcade Race level one.
 Skyline GTR - Win the Kudos Challenge level 5.
 Subaru WRX - Win Arcade Race level three.
 TT Roadster and TT Coupe - Win all golds in Quick Race level one.
 TVR Tuscan Speed Six - Get 100,000 kudos.
 Viper RT-10 - Win the Kudos Challenge level 11.
 VW Beetle RSi - Get 1000 kudos on the easy difficulty setting. 
 Z3 Roadster 3.0i - Win the Kudos Challenge level 1.
 
 Bonus time trial tracks
 Accumulate over three and four hours of game play to unlock more 
 tracks in time trial mode.
 
 Free roam in time attack mode
 Win a silver or gold medal in all parts of kudos challenge mode 
 for a city. Select time attack mode and a "Free Roam" option will 
 be unlocked for that city.
 
 Bonus helmets
 For every hour of game play you will receive a new helmet for your racer.
 
 Medal pursuit paint jobs
 Accumulate five hours of game play to unlock medal pursuit paint  jobs.  
 
 Sliding for more points
 Use the hand brake when going around a turn.

 Custom music:
 You can hear your own Xbox ripped music while driving. Note: You must have 
 already downloaded music to your Xbox hard drive. Before you start driving, 
 enter the option menu and select "Music Management". Select "Add", then press 
 Left or Right until your music appears. Then, add it to the music list. Begin game 
 play, go to CD mode and scroll through the music list below that, on the station.

 Do a 360:
 Start on a wide street (four lanes or more) and get some speed (80 to 100mph).
 Next, get on one of the side lanes and hold A (Hand Brake) while turning into the 
 road to do a 180. Immediately as you pull off the 180 release A and hold X 
 (Reverse) or shift down into reverse, and turn the opposite direction. When you 
 pull around to the direction you were going, release X and go. This requires some 
 practice. Try this trick in time attack mode at Financial District, Federal Reserve, 
 just around the first corner with the Ferorce, Ferrari F50, or the Ferrari 355 FI.

 To do a 360 and get infinite kudos until you stop, get to a wide street with at least t
 the F50 or a very powerful car such as the GT2 or GT Carrera. Punch the gas then 
 turn the car. Keep turning it and release the D-pad until the car keeps spinning by 
 itself. Once you accomplish this, your kudos score will keeping increasing until 
 you decide to stop the car. This may require some practice. Note: You must still 
 be pushing the gas during the spin.

 Do a 540 or more:
 Go at least 140 mph and when you get to a wide section of street, press A and 
 turn Left or Right do a 180. then steer in the opposite direction you were going. 
 Do not press X once you do a 180 -- just steer. Once you do a 360, steer again in 
 the opposite direction to do a 540. You can do as many turns as desired by 
 repeating this process with enough room on the street and enough speed. Try 
 doing this in free roam mode on Wall Street after you get out of the tunnel with 
 the Ferrari 360S.

 Slower opponent cars:
 You can make the cars go slower if you drive in front of them, or you can get 
 them to get away from you by driving next to them.

 Pacific Heights: Big air:
 Enable the "Cheat mode" code. Go to time attack and select Pacific Heights and 
 free roam mode. Select either the Tuscan or the Feroce. During game play, 
 reverse all the way to the wall in back of you. Turn down the hill, making sure 
 that it is a brick road. Drive as fast as possible down this set of hills to get major 
 air and possibly hit a power line.