The procedure is :
-Phisically disconnect the battery ( there are a lot of guides online)
-Now you're abe to have green or blue led plugging the phone in a pc with Flashtool running.
-Reinstall a stock rom using flashmode(green light , pushing the volume up button during the insert of usb)
-Reinstall the kernel ( Doomlord preferably), now don't unplug or push nothing
-This passage is confusional, i tried some times to reconnect the battery after the installation and to send the command from flashtool reboot system. The first times the sony logo appeared only for some second but after some installation and try , worked.
-put in charge for some hours
Hoping that it's usefull for someone
flashtool method form tft file (the first you have to do)
Flashtool method only for kernel(after the tft installation)