When you're doing a search with do=getnew or do=getdaily, it doesn't use the tag parameter. You could change that by editing search.php.
Find this (around line 481):
PHP Code:
//set critieria and sort
set_newitem_forums($criteria);
set_newitem_date($criteria, $current_user, $_REQUEST['do']);
set_getnew_sort($criteria, $vbulletin->GPC['sortby']);
//check for any errors
$errors = $criteria->get_errors();
and add some code like this:
PHP Code:
//set critieria and sort
set_newitem_forums($criteria);
set_newitem_date($criteria, $current_user, $_REQUEST['do']);
set_getnew_sort($criteria, $vbulletin->GPC['sortby']);
if ($vbulletin->options['threadtagging'] && $vbulletin->GPC['tag'])
$criteria->add_tag_filter(htmlspecialchars($vbulletin->GPC['tag']));
//check for any errors
$errors = $criteria->get_errors();
There may be a way to do the same thing just by building a url with the right parameters (instead of using do=getnew and editing the code), but I'm not sure.