TNN Motorsports HardCore Heat

LE-2001 truck:
Press Y, X, Right, Left, Right, Left, Down, Down, Up, Up at
the mode selection screen.

T4 fighter jet:
Press Left, Right, Down, X(4) at the mode selection screen.

Additional colors:
Press Down, Left, Up, Right, X, Y, L, R at the mode
selection screen to unlock a fourth color set.

Random weather in time attack mode:
Press R, X(7), Y(7) at the mode selection screen.

Super expert mode:
Press Left, Left, Right, Right, Left, Right, X, Y(8) at the
mode selection screen.
(Information from Cheat Machine)