Woah!!! Seriously??? 40 Mb (Megabits) per second, download???
Are you using the Speedtest.net app or through a phone Browser that allows desktop mode. Or are you tethered to a PC? Speedtest.net or Speakeasy? A different speedtest site?
I would try all of the above to somewhat confirm your speeds.
I only noticed that to certain servers in the speedtest.net app that it would actually go above 3.5 Mbps. My best through my app was 12Mbps only to one of the nearby servers. Through dolphin or opera browser (in desktop mode) the servers that would only go to 3.5 actually went to around 8Mbps. Also in general Speakeasy has been giving me faster speeds than speedtest.net.
I don't believe there was a change for my speeds except for in the speedtest.net app.