3.1.2/3.1.3 Spirit JB => iOS 4
* iPhone 3Gs (with old bootrom)
* iPhone 3Gs current FW 3.1.2/3.1.3
* already Spirited your device (Spirit JB) ?
* iTunes 9.2
* iOS 4 - Custom created using PwnageTool (hackint0sh won't support Snobreeze)
* Create CustomFW using PwnageTool 4.01
* Lanch Cydia and add repo.woowiz.net
* Install Spirit2Pwn and restart your iPhone.
* Shift Restore Custom 4.0 using iTunes !
I had not tested this. Please do not try this until mods and users confirm this procedure.