I AM NOT RESPONSIBLE FOR DIDDLY SQUAT IF YOU MESS THIS UP TO THE POINT YOU NEED A NEW IPHONE
You need a few things here. They are:
iFaith SHSH blobs saved
iTunes version whatever is current
iDevice running on A4 chip
iOS 5.0.1 firmware
Snowbreeze 2.9.3
iPhonebrowser (optional)
(these things are your responsibility, I will not give download links)
Let's get started
1. Open up snowbreeze and create a custom jailbroken firmware using iFaith shsh blobs
2. Use that firmware to restore to iOS 5.0.1
THESE NEXT STEPS ARE NEEDED IF YOU USE ICLOUD BACKUP
If you try to use iCloud, none of your backups are going to be there. Here's how you solve this
1. Open up iPhonebrowser (Leave your iphone alone at the setup screen, don't touch it. If you get no service issues pop the sim before you get to the screen and wait
2. Navigate to System > Library > Coreservices > Systemversion.plist
3. Save that file to your desktop and open it up with notepad
4. Where it says "9a405" replace that with "9B176" (no quotes)
5. Where it says 5.0.1 replace that with 5.1
5.5. Save the file
6. Right click the systemversion.plist and replace it with the one you modified. You may want to save the original. (reboot after doing this)
7. If you popped out the sim you can put it back in but unplug your iPhone from itunes and do setup as you normally would
8. Replace the file after you're done. (you need to reboot for this to take effect)
9. Enjoy the jailbreak!
This took a while to type and I don't expect it to be perfect. Please +rep if helped and tell me if something goes wrong. I will help asap.