Hi! I see this thread has been dead for quite a while but it’s the closest symptoms to my 2001 expedition 5.4L V8 that I have found so far when researching my problem.
Mine also has a rough idle, big loss in acceleration, it kind of “lurches” at times, gas mileage went all the way to about 5 mpg, etc. Also it has a constant, sometimes flashing CEL light. My scan tool showed two misfire codes- PO303 and 307. Also a pending code PO1405 which i found on here and it said it was a DPFE Sensor Upstream Hose Off Or Plugged.
A few weeks after the CEL light came on and it had the above symptoms, I noticed it was leaking coolant. I saw a very small amount leaking towards the top of the engine when it was running and I had to add coolant to the reservoir.
I thought it was most likely a coil pack or spark plug but does the coolant leak mean something different, or are those most likely two separate issues?