[kh99]

I think you want external.php around line 726 (for RSS2):

PHP Code:

if ($vbulletin->GPC['fulldesc'])
{
    $xml->add_tag('description', $plainmessage);
}
else
{
    $xml->add_tag('description', fetch_trimmed_title($plainmessage, $vbulletin->options['threadpreview']));
} 


so you could change that, or you could add "&fulldesc=1" to the url.