After 2 hours of trying I've figured it out. This community helped me so I figure why not help them back. This is how to restore your iPhone 3GS 4.2.1 with the iPad baseband without receiving an error on iTunes. All credit goes to member Lense on thread http://forums.macrumors.com/showthread.php?t=1057032 post 17. Basically you'll need redsn0w 0.9.6b6 (version I used) Apple iPhone 4.2.1 firmware http://appldnld.apple.com/iPhone4/061-9895.20101122.Cdew2/iPhone2,1_4.2.1_8C148a_Restore.ipsw and a custom restore image http://www.megaupload.com/?d=6JVZF92E ( Reason for this separate post was for awareness and translation to the English language a tad more clear) Use redsn0w and click Browse ( find the firmware image you downloaded from Apple) Select Yes ( at least I had to) In redsn0w select Next In that screen check the box that says "Just enter pwned phone in DFU mode" Phone will now have a black screen, do not worry it's in DFU mode if you followed the steps correctly. Open iTunes, hold the option key (Mac) and select the custom recovery image we downloaded through Megaupload Your phone should now be restored to 4.2.1 and should boot up to something besides the iTunes logo. Use redsn0w again select Apples firmware, this time ONLY select the option to install Cydia. Follow the steps, it will take a while for it to completely boot up. If you get a white icon for Cydia like I did, use redsn0w, browse for the ipsw from Apple, this time select "Just boot tethered right now" Hopefully this helps some of you.