Create a Profile with the Name DIRTY and customize a Honda Civic how ever you like it and store the car. Exit the customize car option and hold Select for 10 seconds (May take Longer). The song "Get Low" by Lil Jon should come on and you will be able to race against him, T.I., Ludacris,Bone Crusher, TrillVille, Young Bloodz,and Pastor Troy in the Underground Mode.