I tried downgrading my iPod Touch from 5.1.1 to 4.1 with no luck. I had errors 1646. 21, 20 and a couple of others. I got the furthest by putting the iPod in DFU (home and power button) with signed 4.1 ipsw (4.1 blobs) through redsnow mac_0.9.15b3 and TinyUmbrella TSS Server on. It did get past the "Verify with apple" in itunes but did not get much farther. What am I doing wrong here?