Easy solution. Google search:
[search term] [search term] [search term] site:asstr.org
Will pull up every story with your terms.
One I'm using on this search engine is:
site:www.asstr.org gbhasext:1 -inurl:index -title:stories <SEARCH TERMS HERE>
in an attempt to avoid returning the index pages where stories are described (they tend to end in / and if not they tend to have index in the title, and the 'repository pages' many times have "stories" in the title, but that is unusual for a an actual story to have.)
I.E. I'm trying to just get one result per story. I will tweak the search engine to identify these repository pages better, it'll spider them but not includee them in the search results. But for now this works pretty good.
There is also a huge weight for the language in an attempt to avoid seeing stories in french. Fairly soon that extra stuff shouldn't be necessary and the search engine should rank stories highly, and repositories of stories lowly.