I have reviewed your database and it looks like this information regarding attachments has already expired and is gone. In SEO, six months is supposed to be the "acceptable" amount of time to support old links, so that people can update the old links. After that time, VaultWiki cleans up data that is not being used (the original IDs still existed, so it was not used).
This means that attachment.php style links, pointing to attachments in wiki pages, will no longer work on your site (the redirection for that expired already) once the original forums are removed. I might be able to regenerate this information from the forums before you delete them. I will let you know shortly.
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In the next release, the importer no longer uses expiring 301s for mapping IDs of imported content (although some alternate URLs for some content, specifically imported islands, will still use them). Instead, it relies solely on the vw_import log for ID mapping, and relies on the admin to choose when to manually shut-off the redirection.