Intermittent P0355 issue

[revolio_gt]

I have a 2016 mustang GT. A few weeks ago on a drive, the car randomly felt sluggish on acceleration, along with an accompanying sound (misfirey sort of sound) which lasted for a few minutes, then eventually went away. But it has continued to come back up every now and then ever since. I managed to scan the code while the car had this issue, and came back as P0355. Interestingly, I have also noticed another symptom whenever P0355 pops up, which is that my AC also stops blowing cold air pretty much every single time. Pretty sure this is because it's gone into limp mode and it turns off the AC as a result. Once it goes away after 30 seconds to a few minutes or so, the ac starts blowing cold again. The check engine light has also only come on a few times when experiencing this, most of the time it silently happens

I have tried the following:

1. Swapped the ignition coil between cyl 5 and 6 to see if it would come up as P0356, but it has remained as P0355
2. Visually inspected the ignition coil connector, couldn't really see anything wrong with it
3. Put in a new battery since my other one was on the way out (also performed the battery management system thing reset), since I thought a shit battery might lead to weird electrical gremlins, no luck though
4. Asked my mechanic about it during my regular service, but they could not reproduce the P0355, so they couldn't really help me

Anyone have any idea what I can try next or what could be causing it? I've got it booked in with a dealership, but I don't really want them to try and push some expensive bullshit on me under the guise of fixing it, so I want to narrow down some of the likely culprits.

The car is also tuned, so if the problem ends up being related to the PCM, it'll be a massive pain in the ass (if I flash the car back to stock, it won't be driveable until I get another tune due to 2018+ manifold, tune-required CAI, non-stock injectors)

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[revolio_gt]

Don’t want to count my chickens before they hatch, but I think I fixed it. In that pic, the left side is raised up a bit for whatever reason. Just pushed it and the wire down, went for a 20 minute drive and no P0355 code or shitty acceleration. Rarely have had 20 mins uninterrupted without at least the code being there in the background, even if I don’t feel it. Will monitor it of course but so far so good.

I stripped that heatshrink/electrical tape/whatever it is back myself to see if there was any breakage btw, didn't look like that originally. put some new elec tape over it