I know this is a setting in the OPSec connection, but I have not been able to find anything on the 1400 WEBUI to set anything in this area. I was also browsing through the CLI guide and there is some stuff about the user awareness, which brought the following question to mind; does you log show the user and URL information, or is that obfuscated as well?
On the other hand when this is an centrally managed gateway you could use the log exporter instead from management, this will give you much more control over what is sent to the syslog server.
Regards, Maarten