How to Successfully Restore iOS 4.3.3 on a Jailbroken iPhone 3GS?

Hello Wally, iTunes error 1604 has nothing to do with the version of iTunes installed on your computer as well as the computer itself. So using a new computer and iTunes will not solve your issue as you will get the same problem all over again. Should you use Sn0wbreeze? No, because PwnageTool is working fine on your Mac. iTunes is throwing error 1604 because the device that you are trying to restore was not pwned. Make sure to put your iPhone 3GS (with iPad’s baseband installed) in pwned DFU mode in order to restore custom firmware successfully. To do that, you can use iREB RC4 to put your iPhone in Pwned DFU mode, if you aren’t familiar with the steps, then you can refer on the tutorial posted below: 

Step 1: Download iREB RC4 for Windows from here

Step 2: Connect your iPhone to your PC through USB cable.

Step 3: Launch iREB and select your iPhone from the list of iOS devices.

Step 4: Then put your iPhone in DFU mode:

• Press the Home and Power button at the same time for exactly 10 seconds.
• Then release the Power button after 10 seconds but continue holding the Home button until iREB detects your iPhone in DFU mode.

Step 5: Now, iREB will start patching the iBoot of your iOS device using Limera1n exploit.

Step 6: Once done, you will see the confirmation message saying that Your device is now in Pwned DFU state.

That’s it! Just simply launch iTunes and restore the custom firmware on your device by the ALT (or Shift for windows users) button while clicking the Restore button.