Some sites may benefit from Pagespeed which is already deactivated by default :
Go into your cPanel, while page plugin XtendWeb Nginx :
Select Domain
Server Settings
pagespeed = enabled
Pagespeed_filter = Corefilters or PassThrough (can cause some issues to some sites)
Save ...
Observe again your waterfall and speed from a server in the USA to see well any difference :
https://tools.pingdom.com
Ony the below test site below will give you the 'Start renderer', which is a very important point in optimization :
http://www.webpagetest.org
Friday, May 5, 2017