Variation in no. of request count at document complete

[pmeenan]

WebPagetest doesn't crawl. It launches a real browser and just records whatever it does.

One thing you might want to try is to check the "Preserve UA string" in the advanced settings to avoid adding the PTST to the UA string in case mod_pagespeed is tying the above-the-fold logic to the full user agent string (though the IE UA strings vary wildly so that would suck).