New member chiming in.
I have a 2011 and have also noticed the 3-4mpg fuel economy drop on my Ecoboost, dropping from ~18 down to ~14mpg in mixed driving. I have also noticed an intermittent fluctuation in what I assume to be the turbo. Under gentle acceleration, I feel the engine seem to cycle power on on off quickly for a period of 4-5 seconds. This cycling is not like a transmission shift, but seems to be the turbo is kicking on and off quickly. Seems strange as I've driven several turbocharged sedans and not had this problem It seems that with the drop in temperature, the issue has gotten worse.
Has anyone else noticed this?