You will need to use the 2.0 MPH downgrader and I recomend you upgrade to 3.40OE-A custom firmware.
My homebrew and emulator recomendations:
Emulators
Snes9xTYL ME
Daedalus.
gpSP
NEOGEO CDZ
NesterJ
Games
Quake PSP
Attack of the Mutants
Squarez
Supertux
SmashGPSP
Bookmarks