This had been released for a while and I had tested it with a PSP Slim. With no new firmware, sticking to 5.50 will means you cannot play many games which requires 6.x firmware. This is where the Prometheus patch comes in. It enable the 5.50 Firmware to run 6.x required games.
Prometheus 3 v2 fixes some bug with the XMB return. Just copy my archive to the root of your PSP memory stick and execute the patch from XMB. You most likely needs a reboot.
Grab it from: