My dealer used the 'live with it' line also. I was totally frustrated with the service department, but gratified when the new car sales manager came out to listen and had never heard it before. He called the 'FSE' Field Service Engineer who claimed it to be within normal operating range for this vehicle. I took it to another dealer for a second opinion, and was told the same thing. It was a Mercury dealer and they added that it is quieter in the MKX because that is a luxury vehicle. OK...$35,000.00 is no longer a luxury vehicle. Guess I missed that memo.
Call ford corporate and complain. Keep calling to see if there is a Technical Service Bulletin yet. The only way it can get addressed is if enough of us stay with it. It is all about numbers. This is the pump ford uses and until enough of us let them know it is not acceptable for all of us, we are left cranking the stereo and wearing earplugs.
Other than that...love the car.