iH8sn0w has just posted a new guide to jailbreak iPhone 3GS (New Bootrom) and iPod Touch 3G / 2G (MC Model) on iOS 4, Old guides didn't work for some people due to iBooty and Sn0wbreeze errors, So in this guide he updated this tools and fixed it.


P.S: Do it on your own Risk, I'm not respobsible for any damage happens to your device, If you are not an Adventurer then better to wait for Comex to release jailbreak for all devices on iOS 4.

Notes:
- For iPod Touch 2G (MC Model) you don't need to have 3.1.2 SHSH Blobs
- For iPod Touch 3G / iPhone 3GS you need to have 3.1.2 SHSH Blobs NOT 3.1.3
- This is tethered jailbreak, which means that you have to Reconnect your device with computer whenever it's turned off to turn it on

Steps:
I figured making a tool would take a bit too long. So, i'm going to write up this tutorial. It isn't recommended for regular users.

**BEFORE PROCEEDING, ENSURE THAT YOU HAVE YOUR iPod/PHONE BACKED UP!**

THIS TUTORIAL ASSUMES YOU ARE ALREADY ON 3.1.2!

Q: Why not 3.1.3???
A: The exploit used is closed in 3.1.3 and beyond.
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WHAT YOU WILL NEED:

* An iPhone 3G[S] or iPod Touch 2G MC or iPod Touch 3-- new bootrom
* 3.1.2 already installed or 3.1.2 installed via SHStarget="_blank"H blobs. <-- Broken blackra1n'd devices will work. (Especially if Spirit messed you up!).
* Payload Pwner-r5
* sn0wbreeze V1.7
* iBooty V1.5
* 3.1.2/4.0 firmware downloaded.
* iTunes 9.2 Installed
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STEP A : Pwning iBoot
I : Download this easy tool here -- Payload Pwner-r5 // It will help you create the payload.
II : Extract it to a directory and run Pwner.exe
target="_blank"
**SAVE THE PAYLOAD WHERE iBooty is.**
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STEP B : Making a Custom IPSW
I : Download sn0wbreeze V1.7 from here -- sn0wbreeze V1.7
II : USE EXPERT MODE!
III : In General, Checkmark "Disable NOR Flash" <-- THIS IS ESSENTIAL!!!!
IV : Build it. It will be on your Desktop.

**CUSTOM BOOT LOGOS THAT ARE MADE IN sn0wbreeze WILL NOT WORK ON NEW BOOTROMS!**
*Mac Users : PwnageTool does not have this option. I don't think it will ever be in there. Use a Windows Virtual Machine or friends PC to create your firmware.*
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STEP C: iBooty Prep.
Most of you know of the utility "iBooty" that I made for Aki_nG.
It will work as long as you place all of the correct files there.
I : Download iBooty GUI here -- iBooty V1.4 and Extract it.
II : Extract your Custom IPSW created by sn0wbreeze with 7-Zip or another un-archiver.
III : Grab the kernelcache and bring it into the same folder as ibooty.
Also grab iBEC from the folder "Firmware\dfu".
Aswell as DeviceTree from the folder "Firmware\all_flash\all_flash.n88ap.production\Dev iceTree.n88ap".
IV :
* Rename your Kernel 4.0-Custom to "kernel.40"
* Rename your iBEC 4.0-Custom to "ibec.40"
* Rename your DeviceTree 4.0-Custom to "devtree.40"
***MAKE SURE YOU REMOVE THE .img3/.dfu/etc extensions!***
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Your folder should look like this :
- iboot.payload <-- Created with Payload Pwner.
- devtree.40 <-- Grabbed from Custom IPSW made by sn0wbreeze.
- ibec.40 <-- Created with Payload Pwner.
- bspatch.exe <-- Comes with iBooty.
- iBooty.exe <-- Comes with iBooty.
- kernel.40 <-- Grab from Custom IPSW made by sn0wbreeze.
- sn0w.img3 <-- Comes with iBooty.
- wait.img3 <-- Comes with iBooty.
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STEP D: Restoring to 4.0 + Booting
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*MAKE SURE YOU ARE ON 3.1.2 WHEN DOING THIS*
I : Run iBooty and Select "Prepare Device for Custom Firmware". Run the Process and if you see the image, you can proceed!
II : Now open iTunes and restore to the custom ipsw.

***WHEN DONE, YOUR DEVICE WILL GO INTO RECOVERY MODE. IT WONT BOOT.***
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STEP E : Booting
I : Just Re-Run iBooty and select "Boot It". If all goes well it will boot!
Warning: This guide is very advanced and not for normal users, So I will say it again, better to wait for Comex to release his new tool to Jailbreak iPhone 4, iPhone 3GS (New boot), iPod Touch 3G / 2G on iOS 4.

If you have done with Jailbreaking your device, then you will be able to Unlock it using Ultrasn0w 0.93 easily by following the guide posted here.