It happens often for me that, after submitting the answer, I look at the "Related" list on the sidebar and see questions that talk about the same question but have a title that's largely difference in words, although very close in meaning.
I know there's a "Similar Questions" list that appears while writing question body, but that's also based on text-processing, which seems to be the problem.
I suggest that, after the user adds the tags, a new "Questions that may already have your answer" list loads right above the "Post Your Question" button, and it depends not only the title and boy text, but also on tag association.
Hopefully it would be not very hard to implement, and would make users life easier.
Questions that may already have your answer
box shows good questions, but they are for e.g. Perl when I need e.g. Python.