Filler neck/tank seal?

[JimRummy]

So I've been having a mystery misfire/CEL that seems to affect everything (mpg, shifting, brakes seem worse, misfiring etc) and through the never-ending hunt to remedy this I've replaced the
Coilpack,
plugs,
added DEI protect a boots (one cylinder has an excessive heat issue, the opposite side has oil leaking into the cylinder, refer to second picture)
didn't replace wires, but they have maybe 6-10K on them, no visible damage
New PCV
New water pump, fan, clutch coolant temp sensor & thermostat (used to have cooling issue)
checked all visible wires and vacuum hoses (replaced one by vapor canister
New oil & filter, fuel filter has maybe 10K on it...

Anyway a few weeks ago I was filling up, and instead of clicking off when the tank was full, it began overflowing, and not at the filler door, it was pouring out underneath the truck ( I know red flag ). I didn't even think about it, but today I dumped a Lucas fuel cleaner I had, and none of it made it into the tank..

I can't feel or see any cracks in the filler neck.. what am I looking at here...

 

[downer]

filler neck rotting off is a common problem. they usually tear at the elbow just above the tank or around the hose clamp where the filler neck meets the tank.
shouldn't cause a misfire. would cause an evap system cel, high purge flow or something like that. the plugs on the other hand..how old are they?

 

[JimRummy]

6-12k on them.

 

[adsm08]

For only having 6-12K miles those plugs look awful. The one on the left looks damaged, and the one on the right is fouled.

 

[JimRummy]

Yeah I know it. The other 4 look good. It's #2 & #6 cylinders, something funky with that bank.
Don't know what's causing it/where to start..
The left one had some serious arcing or something going on.

 

[downer]

the plug on the left would be a symptom of a misfire, running lean, maybe preignition. i'm not a master plug reader though, i'm sure someone else has dealt with this. have you checked that it's the correct plug? and what is the gunk around the threads? was the plug fully threaded into the head?
need to figure out how you're getting oil into the other cylinder, but i'd be more concerned about the burned up plug.

 

[JimRummy]

Yeah. I think it's a bunch of carbon and crap in the threads. Don't know if it is directly from it but I seafoamed her 10 miles before replacing the plugs. All the other cylinders had a tiny amount of soot, nothing noteworthy.
That makes sense, I had MAF fail on me while driving a year or so back. I'm running a junk yard MAF right now which I'm not 100% confident in. Had to run it without a MAF (looking like a diesel with the black smoke) while I was trying to figure out what, and why it was happening (don't mean driving, just diagnostic).
According to Ford-Parts, AutoZone and Amazon they are the correct plugs (and yes, they were definitely threaded all the way), although I do remember the original plugs it had (and I mean rolled off the lot with) lasted like 90K miles were copper, these are platinum.. . I thought I read something saying I could run a double platinum in that cylinder and it would handle the heat or pre ignition better, but I don't know. It does ping every once in a while when starting cold, and up a big hill or heavy load..

 

[JimRummy]

As for the eroded plug in cylinder #3, should I bother getting a double platinum or iridium? Also I can't find a double platinum motorcraft for my truck.. I know autolites are the equivalent, but are they good? Or what about NGK?

 

[downer]

it won't matter what plug is in there if it is really running lean on that cylinder. may want to get the injector checked out.

 

[JimRummy]

Gotta pull it or can I test it on the fuel rail?

 

[downer]

i don't know of any way to check it without taking it out