I’m also experiencing this. I’ve followed the optimization tips in that article with no help. The problem is the Time to First Byte. With the XSTORE plugin enabled it’s between 6-10 seconds! With the Xstore plugin disabled (and everything else enabled) it’s 300-600 ms. It just started happening with the most recent update. I’ve tried disabling all the other plugins and also a different theme. I’ve also tested a plain text file on my server that has less than 300ms TTFB. I’ve tried both with and without a caching plugin enabled. I’m running just this site on a 2GB VPS, should be super fast? Any ideas?