you can't downgrade with a firmware higher than 2.00, anyway there's a trick using the original copy of GTA (that i think is what you were talking about) you gotta use some Eboot Loader thing that works from the images folder
http://www.fanjita.org/ <----fanjita is the guy who made this thing, here you can download the eboot loader and i'm sure you'll find a lot of more infos :wink: