You must have a non-hatchback car available for this cool glitch. First get a non-hatchback car, go to race 77( Time Trial, Samantha's Big Tease ), beat the race to get to reward screen. DO NOT choose Dual GT and Duotek, as they have both saloon and hatchback version and thus won't get you additional spoiler. Instead choose Katana( always ), save the game and exit Underground mode. At Main Menu go check ''customize your ride'' section, choose a hatchback and see Dual GT WILL BE AVAILABLE! Now choose a saloon car you will see not only Katana is available, but saloon version of Dual GT WILL BE AVAILABLE, TOO!

This will happen almost everytime, but if you have extra cash and want to make sure it happens 100%, choose Katana at Underground mode, go to customize car section in Underground mode, trade-in for a hatchback, and trade back the saloon car again, you will see this happening!!

As result, you will see only two kinds of unique spoilers in Underground mode( Katana for saloon and Dual GT for hatchbacks ), but at Main Menu you can find THREE kinds of unique spoiler available( Katana & Dual GT for saloon and Dual GT for hatchbacks ).

Note: due to the glitch, non-hatchback version of Dual GT will stay with your ride's color.