Replace content

Hello,
I need to replace some content from the feed. I use this code (i know it works with function “the_content“):

function replace_content2($excerpt) {
  $replace = array(
	'comments' => 'commenti',
	'submitted' => 'Postato da',
  );

  $excerpt = str_replace(array_keys($replace), $replace, $excerpt);
  return $excerpt;
}

add_filter('super-rss-reader','replace_content2');
/** FIX WORDS */

But it seems don’t works. Do you know which function can I use instead of super-rss-reader?

Thanks.