Share your experience!
How can i know my phone SI and how i can find my firmware origin? i think that my phone is imported but from where? how i can find those information? and if i flash the italian original sony firmware i will lose the warranty? only flashtool and without bootloader unlock. Sorry for my bad english 
contact a Sony Moderator and give him/her your IMEI number and they will be able to help you. (make sure that you send it to PM).
Don't forget to mark the Correct Answers & Helpful Answers
unrelated topic, if you have some time please check this thread
regarding warranty
Don't forget to mark the Correct Answers & Helpful Answers
unrelated topic, if you have some time please check this thread
http://talk.sonymobile.com/thread/44888
From sony mobile developers
http://unlockbootloader.sonymobile.com/instructions
Warning! If you perform this step, you will unlock the boot loader.This may void your warranty and/or any warranty from your operator. If you still want to unlock the boot loader of your phone, enter fastboot.exe -i 0x0fce oem unlock 0xKEY, where KEY is the unlock boot loader key you got in the beginning of this instruction. The boot loader should now be successfully unlocked.
from Sony mobile
Warranty Document
http://www-support-downloads.sonymobile.com/common/warranty_phones_US_12.pdf
Nor does this warranty cover any
failure of the Product due to accident, software or hardware
modification or adjustment, acts of God or damage resulting
from liquid
Update:
For most issues/problems, unlocking the bootloader voids the warranty. Sony Mobile only honors the warranty if it is a known issue in that model/batch of phones or if it is an issue that clearly could not have been caused by flashing a different ROM. Because a new ROM can have a wide range of consequences (e.g., it can overheat the battery or change the voltage, which can damage other components), that basically means that only a small subset of issues are still covered by the warranty. Therefore, even when the phone is in warranty, the service center usually has to do a very costly board swap in order to get the phone back to its original state before it can perform any repair. The end-user has to pay for that part of the repair.
We are proud of providing the unlock feature to the developer community. Previously, there was a large risk of bricking the phone when unlocking with third party software. Sony Mobile’s solution remove’s that risk. When we initially provided the unlock feature, it was presumed that only highly skilled developers and super-users would take advantage of it. From blogs and discussion boards, it was clear that the community understood the risks and that unlocking largely voided the warranty. It appears that less sophisticated users (despite all our warnings) might be using the feature, and are now surprised by the consequences.