Apparently, DevTeam has released Pwnage Tool 5.0.1 which lets you create custom firmware on Mac OS X. Undoubtedly, Redsn0w also provides the same functionality, but the Pwnage Tool is meant for advance users. You can create the custom firmware for iPhone 3GS, iPhone 4, iPad and other A4 based devices. While creating custom firmware, you can do many customizations as per your needs.
Pwnage Tool is classic way of creating custom firmware on Mac. With this version, you can create custom firmware for iOS 5.0.1 and preserve the BaseBand of your iDevice. Once the BaseBand is preserved, you can use ultrasn0w to unlock the device. Ultrasn0w is fully compatibility with the latest iOS firmware. It should be noted that you require Pwned DFU mode for the restore in iTunes.
On Mac, you can use option+restore and shift+restore on Windows. Just browse the cooked custom firmware and select for the restore to proceed. If you come across any error, follow the instructions carefully to enter your device into Pwned DFU mode from the Pwnage Tool. Beside Pwned DFU, there are other modes called DFU and recovery mode which are different from it. So, don’t confuse yourself.
Download link (torrent)