Timing chain stretch, there's a TSB out. I had mine replaced at 50 000 miles. It was a 2011 ecoboost. Lots of info on google about this

 

Manifold leak was an issue on some. I know my 11 had the symptoms when I traded it in. If it's at a dealer see if they will pull dealer service history. Also check the Charge Air Cooler ( CAC) to see if it has been changed. There was a TSB for that and it pretty much took care of the shuddering issue.