Changes from 5.50 U3R:
Fixed PSX Games - they are now working. (tested on Gran Turismo)
Fixed exit with O button - now working.
Added built-in plugins: (only for psp-2000, and still under construction)
LEDControl 0.2 (not working on my 2000)
Hold+ 3.7 (working on my 2000)
MusicPRX 390 (not working on my 2000)

Installation:
1) You must install first 5.50 GEN or 5.50 U3R as a shell (framework).
2) Delete u3rloader folder from /PSP/GAME if it is.
3) Copy u3rloader folder from a zip file to /PSP/GAME
4) Start 5.50U3R Installer from Game - Memory stick.
5) Click X to install firmware or Up with plugins.
6) Enjoy!