Enter the following as passwords:

YRDR		Low rider trucks
Y_WNT_T 	Full-time missiles
JMPNG       Changes graphics & textures
CFFNYN      Turbo Mode
BRPS        Gut Bomb

Aztec Valley Track:
Beat a circuit under Easy difficulty.

Alpine Challenge track:
Beat a circuit under Medium difficulty.

Death Trap track:
Beat a circuit under Hard difficulty.

Noises:
Press Up on the D-pad for burps and farts, and press Down on the D-pad for different honks.

Level Passwords:

BEGINNER
--------  
Ruins                   G[Up Arrow][Star]NJ2L0 
Junk Yard               J[Star]XQYN4G 
The Heights             M[Star]OT1Q9R[Left Arrow] 
Voodoo Island           P[Left Arrow]3W4TC[Star][Left Arrow]F[Up Arrow] 
Greenhill Pass          5[Up Arrow]627WFX9[Left Arrow]23G 
Wasteland               V[Left Arrow]92[Up Arrow]2[Down Arrow]0CL56B5V 
Aztec Valley            YYC5D2L3F[Right Arrow]89[Down Arrow]8[Right Arrow]B7 
   
INTERMEDIATE
------------ 
Ruins                   GBGJ5MTL 
Junk Yard               JNJMQL7S 
The Heights             MJMPT[Right Arrow]XRN 
Voodoo Island           PJPSWR0[Star]89R 
Greenhill Pass          SBSV2[Star]3XBC[Up Arrow]4[Down Arrow] 
Wasteland               VBVY2X60[Down Arrow]FD7B2M 
Aztec Valley            YFY15093H[Left Arrow]G[Up Arrow][Down Arrow]5675 
Alpine Challenge        1N1483C6KLJDH89[Up Arrow]G4N 
   
EXPERT
------  
Ruins                   GKGH[Up Arrow]G[Star][Left Arrow] 
Junk Yard               JGJKLJP[Star] 
The Heights             MSMN[Right Arrow]M7QW 
Voodoo Island           PKPQRP[Up Arrow]T793 
Greenhill Pass          SKST[Star]SDW[Up Arrow]C61R 
Wasteland               VOVWXVGZDF9463R 
Aztec Valley            YGY209YJ2G[Left Arrow]C796462 
Alpine Challenge        101231M5JLF[Up Arrow]C979S0D 
Death Trap              404564P8M[Right Arrow][Left Arrow]DFC[Up Arrow]CV32KC"

Thanks to Revolution readers pat, Corey Brown, Jack DIllmann, Drew Cambell, Eddie, len, Ryan Thurm, Sufyan, Eddie, Chris Amato, Jeff McPherson, Josh Poisson, Scott Meyer, and Magic Sal!