Thought I fixed misfire/stumble remains

Misfire on #1 due to old plugs and crack in coil housing.

How did the old plugs look?
Try a bottle (or two) of Techron in the gas tank.

Misfire on #1. Crack in coil. Next step.

Have you swapped the coil packs?
If the misfire doesn’t follow it’s maybe time for a compression test.

Worst how? Black soot? Deposits?

Oh, got a new coil pack. Problem is fixed on rear bank for plugs 1-3-5… The #3 coil plastic was cracked at the base of the rubber boot but the #1 plastic looked ok and the misfire was on #1. So, there is that. A crack is not absolute proof there is an issue. But it kinda leans that way.

In my opinion . . . any coil that is physically cracked can’t be trusted

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I’ll go a little off-topic

I’ve seen lots of problems caused by 4-electrode spark plugs

Usually in engines that weren’t designed for them

Vue website said use Bosch+4. Got 8yrs of good service. Put in dbl platinum now. Misfire on #1 is gone. But I got front of motor wet and have misfire on #2. So, I just pulled front coil. Yes it has cracks on 2 of 3 plug bosses. Ok. Life is like that. Replace coils in pairs.