If you have the blobs to downgrade, download the IPSW that matches the blobs that you have, download the latest version of RedSn0w (0.9.15 beta 3). Go to your host file, delete any gs.apple.com lines in there, and delete the Host.Umbrella file as well. Flush your DNS. Run RedSn0w as ad administrator, go to Extras > Even More > Restore. Select IPSW and point it to the IPSW that you downloaded. Then for blobs, select Remote so RedSn0w will retrieve them from Cydia. Then click Next. Say Yes that you're aware that your baseband will be upgraded and that your data will be wiped. Make sure you back up your device before doing so. Let the device restore. It might not be necessary, but if it doesn't work the first one or two times, run TinyUmbrella and start the TSS Server before running RedSn0w. After the restore, chances are you're going to be in Recovery Mode. Use a Recovery Fix in RedSn0w