I ordered a psp from japan and it's coming in with 1.5 firmware. How do I go about installing 3.40 oe-a into it? Do I use the japan 1.50 or the US 1.50? Which 3.40 do I use? US or Japan? Has anyone tried the custom firmwares on a japanese psp? I realy don't wanna use an outdated devhook.