GT Advance 2: Rally Racing Codes -

All cars:
Hold L + B and press Left at the title screen.

All tracks:
Hold L + B and press Right at the title screen.

All tune ups:
Hold L + B and press Up at the title screen.

Extra modes:
Hold L + B and press Down at the title screen. Alternately, complete all the tracks in each class of championship mode to unlock one option. To unlock the Wire Frame mode option, successfully complete all the tracks in each class of championship mode under the expert difficulty setting.

Expert championship mode difficulty:
Successfully complete the championship mode with a Gold rank on all tracks under the normal difficulty setting.