Metropolis Street Racer cheats and cheat codes for Dreamcast

Unlock all tracks: 
During the intro, hold Start.

Humvee and Ambulance bonus cars:
During the intro, hit A, B, A, Up, Down, Y, Left, X 

Unlock all Cars
From the Title screen, press a, x, y and R simultaneously.
The cars will appear in your saved game.

Honda S2000: Finish Quest mode once
Porsche 911: Finish Quest mode twice

Unlock Free Roam mode for each area of the 3 cities:
Win all One on One Challenges in Chapter 25

Opel OPC
Finish the Special Stage in the 9th level of Chapter 3.

Adjust Camera Cheat
Finish the Special Stage in Chapter 8.

Unlock London Cab
Finish the Special Stage in the final level in Chapter 6.

Chapter Cars:
Finish the following chapters to unlock new cars: 

Chapter - car:
1: Opel Astra 
2: Renault Megane 
3: Alfa Romeo Spider 
4: Peugeot 206 
5: Peogeot 406 Coupe 
6: Toyota MR2 
7: Peogeot 306 
8: Mercedes-Benz SLK 230 
9: Alfa Romeo 156 
10: Audi S3 
11: Alfa Romeo GTV 
12: Audi TT Coupe 
13: Toyota Celica'99 
14: Fiat Coupe 
15: Mitsubishi FTO 
16: Mitsubishi Eclipse Coupe/Spyder 
17: Opel Speedster/Vauxhall VX220 
18: Mitsubishi 3000 GT/GTO 
19: Toyota Supra 
20: Nissan Fiarlady Z Coupe/Convertable/300ZX 
21: Nissan Sylvia/Sylvia Varietta 
22: Ranault Clio 24V 
23: Mazda RX7 
24: Mitsubishi Lancer Evolution VI 
25: Nissan Skyline GTR