Cheat codes:

fleeting                  All cars 
weflipped                 Mirrored Tracks 
twinpeaks                 2x Height 
ethanol                   Blurred mode
glycerine                 Nitro boost 
T2                        Chrome cars 
krazykerbs                Exploding curbs 
vanishing                 70's springs 
gruntsome                 Extra power 
madcab                    Invisible car 
europa                    Low gravity 
rearfear                  Race backwards 

Unlock cars:
     Collect  the  indicated  number of points in Championship mode to
unlock the bonus car:

Audi TT                   15 points 
Ford mustang GT           30 points 
Plymouth Prowler          50 points 
Celica GT4                75 points 
Dodge Viper               105 points 
Lotus 34CR                140 points 
Mitsubishi GTO            180 points 
AC Superblower            225 points 
Subaru Impreza WRX        275 points 
Mazda RX7                 335 points 
AC Aceca                  400 points 
TVR Cerbera Speed 12      470 points 
Bently Hunaucieres        545 points