Need For Speed Carbon: Own The City Codes -

Unlimited nitrous:
Press (x2), , , , (x2), at the main menu.

Cars:
Defeat the indicated person by finishing first in their race to unlock the corresponding car.

Aston Martin DB9: EX 
Audi TT 3.2 Quattro: Poorboy 
Ford GT: Clutch 
Ford Mustang GT: Poorboy 
Mazda RX-7: Arjen 
Mazda RX-8: Perimeter Sprint 3 in Lucky Sevens 
Mercedes-Benz SL65 AMG: Clutch 
Mitsubishi Eclipse GT: Perimeter Sprint 3 in Lucky Sevens 
Mitsubishi Lancer Evolution IX: Layla 
Porsche 911 Carrera S: MK 
Subaru Impreza WRX STI: Layla 
Toyota MR2: Arjen 
Toyota Supra: MK 

Performance parts:
Defeat the indicated person by finishing first in their race to unlock the corresponding performance part.

Tier 1 performance parts: Arjen 
Tier 2 performance parts: Poorboy 
Tier 3 performance parts: Layla 
Tier 4 performance parts: MK