If you don’t have xbox live, just keep scrolling down.

there is a way to get any car in the game at anytime in the game.
First, go buy some microsoft points
Next, go to the car you want (its ok if its locked)
click purchase and it should say:
“you have insuffecient funds, would you like to purchase with microsoft points”
click yes, the bugatti is 250 microsoft points and the Mclaren F-1 is 240.

FAQ:

Are the cars you buy with microsoft points avaliable in career?
A: Yes. i doesnt matter how complete you are with the game, you could be 2% and have the bugatti.

What happens to the cars if i start a new game?
A: the cars are saved to the hard drive once purchased. they are under the NFS undercover file and they are saved unless you delete them or they become corrupt.

Isnt that cheating?
A: HELL NAW!!

Enjoy!