Engine running lean?

There is a know problem with the O ring seal on the intake manifold tuning valve, it leaks and causes the lean codes P0171-P0174.

This guide can help fix it as well

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Please run down this guide and report back.

That's a definite problem with newer cars, a lot of mechanics, good ones too, are not necessarily trained in diagnosing and repairing newer vehicles, mostly pertaining to areas of electronics, computers and such. It's a very large cost to buy and maintain these diagnostic machines plus the continued training on all types of vehicles. This is not a knock on any mechanic. Most are very good at the mechanical ends of vehicles. There have been problems with pcv valves and related hoses causing lean conditions. Hoses develop pinhole leaks.

P0171/P0174 A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

* TIP: On many Fords, a P0171 and/or P0174 Lean Code may sometimes appear because of a bad Differential Pressure Sensor (DPFE). This sensor monitors EGR flow, and is located on the engine near the EGR valve. There are two hoses that connect the sensor to the tube that runs from the exhaust manifold to the EGR valve. The sensor misreads EGR flow and the computer increases EGR which has a leaning effect on the fuel mixture. The fix is to replace the DPFE sensor

That means that both banks of cylinders are running lean. Too little fuel for the amount of air being used.
1) you might have several plugged or partially plugged fuel injectors
2) your fuel pressure might be weak
3) i've seen the same check engine code in vehicles that have wide open cold air intakes that use a MAF (mass air flow) sensor housings that are not stock. It screws around with the computer's calibration.
I hope this helps some.

You have vacuum leak most likely the intake manifold gasket

Check compression and injector pulse

Post the code or codes here, someone will have ideas. Some of the lean or rich codes require extensive testing, ocassionally, to find the cause. Always start with the simple things, hoses, connections, make sure everything is in it's place. Those pieces you've replaced, were they faulty or you just did it hoping to solve your problem? I don't like to see people wasting $$$$ on parts not bad. Sometimes after doing the easy checks, it costs less to have it diagnosed, unless your local shops are well-versed and well-equipped, as you've apparently sampled a couple who were not, the dealer may be your best bet. Same thing I've been posting forever.

Not likely or will effect all cylinders
pluse cam and or crank sensor related codes
you can check using scanner if timing in SYNC

It means that the O2 sensors are telling the computer that the engine is not getting enough fuel. Either this is tru, or both sensors are bad. Start with a tune up and go from there.