Vivvo is a CMS option for xenforo now.
For sake of completeness, I wanted to mention it in a few of the major CMS threads.
But I can't search for CMS.
I've suggested that 3 letter words should be allowed for TITLE searching. Maybe not even for all three letter words, but certainly some. Maybe the admin could choose which ones would be allowed ?
Another idea might be to forward the search to google as opposed to telling the user the search could not be done.
ie. if someone searches for CMS ... give them this result
Google Search: CMS site:xenforo.com