JMHO Joe.
You didn't mention any SES light flashing briefly or on, so I take it to mean "NO"?
Do you have the OEM injectors? If yes it could be the signal for the end. I don't know all the symptoms. When mine went they gave no warning that I detected. They were fine, I got gas, upon restart they were junk.
Fuel filters in C4's seem to be a bit of a mystery. I do mine every year. Okay, like back in the old days
How is yours? Oh, along that vien. Do you run the gas down really low? I thinking trash in the tank sticking to the sock type of deal? If you know the filter is clean the pressure test is a bit more valid when done, JMHO.
Your narrative about the gas fill ups is/maybe a clue. Runs fine now on this last fill up? It has had the benifit of gas treatment x2...see what I'm talking about? Goes back to the trash in the tank idea.
If it was coils or plugs or wires....it don't fix itself. It's fine now, right?
Just some thoughts for you.
Tom