yeah, like he said, some codes would really help narrow it down
meanwhile, it never hurts to make sure you are up to date on periodic maintenance: change the fuel filter if it has not been changed in the last 30K miles, make sure the air filter element is clean, clean the mass air flow sensor (use proper MAF sensor cleaner) and consider cleaning the throttle body
Does the engine run smoothly? Mine vibrated the interior very badly, but when I looked at the engine while it idled it appeared to be running smoothly. The RPMs did not fluctuate. No codes. Turned out to be failed motor mounts. The motor did not shake or move that I could see, but the bad mounts let the vibration get to the interior. The two engine side mounts have a hydraulic component. I'm not sure how that works but they are not just blocks of rubber. Only buy OEM Ford mounts if you decide to replace them. When I went to change them one center nut on the mount was loose. Maybe try checking the torque on those.
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