hi
first to flash your phone you need :
a software:FARmanager+JdFlasher plugin (To flash CID53) and:
MAIN file
FS file
and a CUSTOM file
and before, for more security do a GDFS backup (use xs4.1 for linux: you are CID53)
for more and detailed informations have look in Tutorials - Top Sony Forums
and also generaly in 'Mark forum read'
;)