QUOTE(cookie man @ May 9 2008, 02:38 AM)

The only solution to downgrade from 3.90 M33 is to use PAndora's Battery
Hmm, it sounds like you are thinking about 3.90 (official).
From any custom firmware (including 3.90 M33) on a 'phat' PSP, you can
downgrade to 1.50 via Recovery Mode.