So I have been trying to get my iphone 4 restored and I am having some issues. Trying to restore it to 4.2.1
When I try to restore while running the TSS Server in TU, I keep getting an error 1600. And yes, it is the stock firmware I am trying to restore in both pwnd DFU and restore mode, same error.
I tried fixing my host file and removing all instances of the apple servers, and when I try again, with the same 4.2.1 fw, I get 3194.
You can use Snowbreeze or Pwnage tools to build it. You have to put iphone into pwned dfu before restoring to custom firmware and you will need tss server to verify your blob.