I have during the last months been fighting to get a better response time on my site until I stumbled upon this one:

WebPageTest

From the webside:

This tool lets you test web pages that are directly accessible as an URL from the Internet. If you need to test a page inside of a firewall or something more complicated than a web page (an authenticated product like webmail for example) please download the desktop version of PageTest which this is based on.

It was very interesting , and after performing the test a few times (from different servers), the responce time went down from (worst case) 17 seconds to 4 seconds after a few mods to my WordPress installation.

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