XF 1.3 Migrate from Phpbb to Xenforo

Since I switched to Xenforo I think I made a mistake some where. Because I'm having things like this show up http://www.hvaclounge.com/viewtopic.php?t=72&p=351

and in google webmaster tools I now have this message:
Google detected a significant increase in the number of URLs that return a 404 (Page Not Found) error. Investigating these errors and fixing them where appropriate ensures that Google can successfully crawl your site's pages.

How do I go about fixing this?