I have a dilemma with my 2011 Ford Edge Limited FWD 3.5L, 113,000 miles. About 2 weeks ago the Edge started having hesitating either going up a steep hill or under heavy acceleration loads (Over 4,000 RPM's). The checking engine light will start to flash and the engine will run rough, but when the light stop flashing the engine ran smooth again. When checking for the engine codes, I retrieved 2 check engine light codes P0420 (Catalyst System Efficiency Below Threshold Bank 1) and P0301 (Cylinder 1 misfire). Now originally about a year ago I did a spark plug change at 100,000 miles, I know I should have change the coils but they were out of my budget at the time and the engine was running great. Then a week ago I decided to replaced all the spark plugs with new Motorcrafts, replaced all the ignition coils, replaced the Catalyst sensor and checked for vacuum leaks. After completing this I had the engine codes erased. The Edge started up great and sounded great. But when I drove it under a load, the check engine light started to flash. The engine code was again P0301. I took the intake off again. Removed all the coils and plugs. I did a compression check and all the cylinders were all good. I checked the fuel injectors and they all were clicking. I decided to replace cylinder 1 fuel injector. After putting everything back together, check all the electrical wiring and I switch the coil/spark plug to cylinder number 4 (just to see if the problem changes code) I cleared the codes and test drove under heavy load and again the check engine light flashes. Ran the codes and it was again P0301. So I called an old friend of mine who is a Ford Master Senior Technician. I explained everything I did. He said 99% of the time it is usually the coil or plug. Then the fuel injector. He said the Ford do have issues with the PCM and I may need to have another one put in and reprogrammed to this vehicle Vin codes. So I ordered a refurbished PCM from Flagship one. I installed the PCM and had the PCM reprogrammed with an updated Ford program. After that was complete, the vehicle ran great. I drove it and even under heavy load, no flashing engine light. I was happy but then after 15 minutes of driving and return home up a hill the check engine light started flashing. I ran the code and again P0301. I am out of ideas. Same symptom's as before, go up a hill or under heavy load, flashing check engine light and engine runs rough, engine light stops flashing, engine runs smooth. I thought maybe the fuel pump pressure could be low but I would think it would cause other misfire codes. Any ideas? Otherwise I am going to have to take it to the dealership.