You do not mention if constant, with engine running at idle, or only when in gear, or only when traveling, Blower ON/ OFF, etc, but a few points: 1) Belts can make weird noises from rust that accumulates on pulleys during moist weather, but many of these will disappear after some miles, (but have also read ads that imply the quality of the serpentine can greatly affect belt noise?); 2) If the 2006 Ford still uses vacuum A/C/ Heat Controls can make strange noises if hoses leak; 3) I had a strange dash BUZZ (like a BEE or bad speedometer cable, but vehicle was electronic dash) that developed on a 94-Nissan Pickup at highway speeds when vehicle was 1-2yrs old that dealer could not find, and finally, after 6-12-months, I tightened (maybe only 1/32-1/8-turn) every nut/ screw on the engine side of the firewall, and it CURED the issue
4) HAS A MUD-FLAP FOLDED BACK AGAINST A TIRE, (e.g. pressure-washer) NOW RUBBING ON TIRE WHEN MOVING? 5) Power steering fluid-level? LUCK TO YA