[Adrian Schneider]

This will add a query for each post displayed... (bad idea)

Use $this->registry->db instead of $vbulletin->db, as $vbulletin isn't available inside of classes. Don't use mysql_fetch_array; instead, use $this->registry->fetch_array()

You are probably better off editing the template cache dynamically rather than modifying the post count value, because from the looks of it now this will break your HTML a little...