There are no official cheat codes for Grand Theft Auto: Vice City Stories on PSP—the PSP entry in the Vice City universe. The classic Vice City (2002) was never released on PSP.
For the full cheat experience (classic codes like "THUGSTOOLS", "PRECIOUSPROTECTION", "BIGBANG"), play Grand Theft Auto: Vice City on:
Enjoy the story—Vice City Stories has one of the best narratives in the series, even without cheats.