Enter the cheats in the "Options Modus" -> "Cheat Codes"!

All cars:                     hotwired
Note: You must be signed into Xbox Live! For this code to work.

All locations:                theworldismine
Unlimited nitrous:            zoomzoom4
Note: This also adds nitrous to motorcycles.

Guns and rockets:             lovenotwar
Play in arcade mode, then click the Left Analog-stick and White to fire.

All car abilities:            greasemonkey
Unlock "Most Dedicated" stat: bigbrother
Adjust game speed:            howfastcanitbe#
Adjust game difficulty:       howhardcanitbe#

#= a number from 0-9