try this edit in your index.template.php
echo '
<title>', $context['page_title_html_safe'], '</title>
i'm guessing in your modified file it will be then?
echo '
<title>', $context['page_title_html_safe']. ' - ', strpos($context['page_title'],$context['forum_name']) === false ? $context['forum_name']. ' ' : '' , '</title>';
$custom_text = 'My Custom Text';
if ((empty($_REQUEST['action']) || $_REQUEST['action'] == 'collapse') && empty($_REQUEST['board']) && empty($_REQUEST['topic'])) // on homepage
echo '<title>', $context['forum_name'] ,'</title>';
elseif (empty($_REQUEST['action']) || !empty($_REQUEST['board']) || !empty($_REQUEST['topic'])) // on board or topic
echo'<title>', $context['forum_name'] ,' - ', $custom_text ,'</title>';
else // if not on homepage or board or topic
echo '<title>', $context['page_title_html_safe'] ,'</title>';
echo'