My apologies if this topic has a thread already but I've tried searching and didn't find anything that suited my needs. I've a non-jailbroken 3Gs running on the battery sucking iOS4.3.1. From what I've read, the new update doesn't solve the ridiculous battery drain. I want to downgrade my 3Gs back to iOS 4.2.1 which I still have the "iPhone2,1_4.2.1_8C148a_Restore.ipsw" file that was moved to the thrash when I upgraded to 4.3. Is it possible to restore it back to 4.2.1 with the above mentioned file & if yes, how? Thanks in advance.