I own a iPhone 4 GSM Model A1332 with iOS 4.3.5. Jailbroken THETRED and Gevey SIM Ultra to unlock the carrier.
Baseband: 04.10.1

I want to upgrade to 5.1.1 (unthetred) but itunes gives a error every time!!!
I created a costume IPSW on sn0wbreeze to prevent baseband update. (If i upgrade the baseband, Gevey SIM doesn't work)
I try everything I read in Mac and in PC:

Method 1:
- Editing host file
- Put iPhone in pwned DFU
- Itunes - Shift+restore
Error 3014 or "the iphone could not be restored its not eligible for requested build"

Method 2:
- Open tinyumbrella, start TSS server
- Put iPhone in pwned DFU
- Itunes - Shift+restore
Iphone enters in recovery mode but... Error 11

I try this operations various times with different variations both in MAC or WIN.

The only thing i could do successfully was to restore the iOS (4.3.5) with redsn0w. It erase all data but now the iPhone it's not activated.

I even try to install a older version of iTunes like a read in some posts but nothing work.

Can someone please help me to upgrade iOS?