How do you unlock tier 3 cars in need for speed undercover?

you have to finish the mission mystery job. in mystery job you will be riding a Nissan skyline. if you do finish it it says you can go to tier 3 shop. you can get tier 3 cograts.i recommend buying a skyline its good. but if you want Mitsubishi IX or lancer you can win it by a pink slip. this is what i done for ps3