Russian PSP hacker mc707 has released EBOOT Patcher v1.0 for Sony's PlayStation Portable, which will allow you to play 5.55 / 6.00 games on 5.00 M33-6, 5.03 MHU, 5.03 GEN-A and other Custom Firmware.
According to French site PSPGen (linked above), Yoshihiro has made available a PSP Game Decrypter which allows users to run new PSP games on older PSP Firmware.
Prior to this, without a new PSP Custom Firmware update available those unwilling to upgrade their official PSP Firmware have been locked out of playing a lot of the new PSP games.
iKest has discovered how to uncensor the new version of Manhunt 2 on the PSP. The process requires the iSO of the game, small deletion of some strings and a replacement of some files as detailed below:
1. Open ISO in UMDGEN 2. Extract PSP_GAMEUSRDIRGLOBALLVLSETUP.INI and PSP_GAMEUSRDIRLEVELSA01_ESGLVLSET.INI
3. Open this files (with notebook) and find: