Cache-Control:public, max-age overwritten

[Re Style]

Hi, I'm testing the pagespeed module on my site. With .htaccess I specify the max-age to a month with the page speed module off I get a score of 94% on gtmetrix.

<FilesMatch "\.(xml|txt|css|js)quot;> Header set Cache-Control "max-age=2678400, public" ExpiresDefault "access plus 1 month" SetOutputFilter DEFLATE </FilesMatch>

When I enable the pagespeed module and run the site on gtmetrix my score drops to 84% and I get the warning that browsercaching is not enabled for the javascript files (5 minutes).
I tryed the following options but none did the trick:

• ModPagespeedModifyCachingHeaders off
• ModPagespeedEnableFilters extend_cache
• ModPagespeedDisableFilters extend_cache
• ModPagespeedForbidFilters extend_cache
• ModPagespeedForceCaching on

How can I enable the leverage browser caching with page speed module on?