Unfortunately, When using the vBulletin default search, this option limits the size of indexed words. The smaller this number is, the larger your search index, and conversely your database is going to be. Webforumz has this limit set to 4 which requires all words within your search to be up to 4 characters. I will talk with Rob about this and see wither he is willing to change that number, although, that might make the site even slower then it already is!