2007 5.4 Flex Fuel, 71,000 miles.

2 years ago had two coils replaced and all plugs replaced by dealer knowing that the spark plug issue was there. They had no issues apparently removing/replacing the plugs.

In the last 6 mos or so I've had a gas smell while sitting at a red light or in a parking place. 10 days ago my wife calls me and says its idling with a low engine RPM wobble and the CEL is on. She returns home.

I plug in my OBD scanner with Torque App. I get a P0304 and P0316. Cylinder misfire on #4. I go an remove it. The bottom 1/5 of the outside of the rubber boot is covered in a grayish material. The spring coil looked dry with a faint smell of gas. I replaced the coil and the engine was good for all of 2 hours. No low end wobble at 600 RPM, nothing. Then it came back. We drove it this past week and then it got worse. Plugged in the scanner and had P0304 and P0308. I replaced #8 and the boot was good. Dry no moisture. P0308 was cleared and has not come back.

I pulled #4 and it was covered in carbon build up and the spring coil has black bits on it with gas. It looks like it has been in there for years and its 10 days old.

I'm wondering if the injector is stuck open or the plug is bad. I stuck a straw down the sidewall of the plug well and it came back filled with about 1/8" of carbon like sludge.

The coils replaced in the last 10 days were not the ones replaced 2 years ago.

Thoughts please.

I searched but with this issue I could read for hours in circles.