I hope nobody minds me raising this from the dead. I found this thread via a google search for the name of the mod that was causing this problem. The offending file in Immersive Armor is iastartupquestscript.pex found in Hothtrooper44_ArmorCompilation.bsa The offending line in the source file iastartupquestscript.psc is line 112, specifically "UlfricRef.RemoveItem (ArmorGag, 1)". You can comment out this line, recompile the script, and leave the recompiled script in Data/Scripts. Ulfric will then have his gag back in the openning scenes and it will be removed as normal once in the keep after the dragon attack. I'm guessing the mod author simply misunderstood the reason for the gag being there (so Ulfric can't use the shout he learned), as it's clearly done delibrately, but doesn't match main quest lore in any way.
