My wife's 3GS is on 4.0 and I'd rather have it back on 3.1.3 and jailbroken. Back when 3.1.3 had come out, I jailbroke it and am sure that the SHSH is backed up on Cydia. But when I try to restore to 3.1.3 in iTunes, I get the error codes. I edited the file in the etc folder (PC) as per iClarified. Am I missing something super simple? Thanks!