Q: my car is hesitant to accelerate when changing down to second gear uphill and sometimes it just won't accelerate.

Hi there. What were the diagnostic results? What were the data readings from the ECM? What diagnostic process did you use to determine the other parts were in need of replacement? These are the questions that I ask anytime I am presented with a unique concern such as this one. Compare data reading to factory specs before replacing any parts; air flow meters can be presenting incorrect readings that are not considered faulty readings. The ECM will simply adjust fuel trim to compensate. Of course, the meter may not be changing the reading at all from idle; imagine how the ECM will react to increased throttle opening with an airflow reading that matches idle speed (lots of throttle and no air) or increased airflow without an increase in throttle position if the TPS is faulty (lots of air and no throttle). I suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a car has low power inspection.