I tested this example and it seems to work fine: http://jsfiddle.net/txhi/9a5m4hfd/
It shows only the items that contains value as in the filtered value.
Could you provide an example with your scenario?
If you want to filtering with specific searching mode then you could use some of the searchMode options (as containsignorecase).
This is a default behavior.
If you could override it then I would like to suggest you try to use the renderer(index, label, value).
This will be useful for your case.
Please, let me know if you have trouble with this implementation.