well i was browsing on the playstation website going through the G.A.P. blogs(which i am a member of). I found one that is new and it said New DOwngrader for 2.0+ PSP's. :Jump: it onbly works on US and AUS PSP's though so watch out. I havent tested it. just giving the site to see if it could be true.
this is the site where it was found.
try it out and see what happens