I've been struggling with this for awhile. CM11 and every AOSP ROM I use on S4 causes a bad echo while using a bluetooth ear piece for anyone on the other end. TW roms like hyperdrive work fine as long as I disable noise reduction/suppression. Does anyone know if there is a fix for this? I really would rather use a bare bones or slightly modified AOSP ROM then the bloated samsung hackup ROMs.