bro its easy just use the process that you used from 1.5 to 3.03oec.no need to go down to 1.5 again.just copy the two folders into your game150 folder then disable all prx then run it in your game menu and wallahhh.you now have 3.40oea.btw you can get the files here
http://www.pspmod.com/forums/showthread.php?t=17548 (help....noob..)
just follow the noob guide there and youre on your way to 3.40oea.good luck bro....