Since you are getting the P0171 and P0174 code, you should start by checking for intake leaks. If there is abosolutly no intake leak, then you may have to replaced the O2 sensors.
P0171 FORD - Fuel Injection System Too Lean Bank 1
Read more: http://engine-codes.com/p0171_ford.html
P0174 FORD - Fuel Injection System Too Lean Bank 2
Read more: http://engine-codes.com/p0174_ford.html