Hi,

You say you have changed just about everything that is supposed to be plug and play.
From the video I have to say the engine is running very rough but at the same time very evenly.

Once past initial start up and late in the warming up time you are saying it gets rougher until it looks like the video on Turbo Bricks. That is a definite roughness but very consistent in my experience.

It appears to be very lean all across the spectrum of ignition and combustion firing.
What ever is wrong effects the whole in and out process of combustion.

Let say that the fuel delivery system is working just fine, but the air mixture turns worse after the ECU moves off its startup program. The one where it ignores the O 2 sensor because it’s not hot enough yet to do any good.

The ECU goes with a preset richer mixture and timing sequence until it gathers up a reading from that O 2 sensor.
It should be working with the ECT and the AMM on the intake side.
IF you have a air leak from or on the AMM’s backside. If so, that input is almost useless.

The mixture needs to lean out past start up quickly and the spark timing will always be jumping around a little bit if the rpm isn’t stable. The ECU is self tuning, of a sort, but in the blind.
You have not, that I have seen addressed the throttle plate adjustment and if the accordion tube from the AMM is completely sealed up.
The intake manifold is easy to put a gasket under but you could have a wire under one edge of one of the intake runners. I have almost done that myself. There are one or two loose wires slipping around when things are undone during a major repair.
Art suggested checking the nuts but “it just might” be more involved than that by an accident.

If the gasket hasn’t been run all that long you might get away with pulling it back for an inspection and see if it has been compressed evenly.

Another thing you have not said anything about is the original spark coil relay behind the battery.
If its wiring is not in the greatest shape the signals from the ICU can get delayed or if the component itself is aged it can not be firing the plugs in a changing time frequency of dwell to the coil.
Resulting in variations of spark durations and likewise false combustions
I know it sounds like a long, long shot but I personally would like to rule it out.

In my other post I did that as the last thing before going off and blaming the ICU and the ECU that you have already done.

As far as the spark plug wires 310 ohms is a very low reading. Maybe you have solid core wires I don’t know but a 8 to 11,000 ohms is stock for radio frequency suppression.
Even the spark plugs can come with resistance values for the reasons of the high voltages.
In my experience running sparks plugs other than the stock silver streak set and a .028 gap is asking for odd performances when nothing else can make sense.
What are you using?

I’m not ruling out any of basics of the the three sided triangle of combustion.
I will say you are rattling around on some very slim choices of what else can be going on with this engine.

I truly believe there is a basic “honest to gosh” simple reason.
I’d stress start with the ignition and then the air.
There’s a point where the two sides of the triangle touch.
No matter which way you way you spin the rod to make it ring, Meal time! 🤩

The electronics is just twisting the puzzle as best it can! It was designed that way.

Ignition is the oldest (135 years) of a simple technology. Wires were of flat copper or brass strips of metal.
Solid core Silicon Racing wires the latest buzz …really?
The ignition systems are depended on the heaviest and now with unbelievable RPMs past mechanical points.
We still use “jump a gap” rotor buttons. Copper terminals caps were a better choice so I hope you have them as well.
I cannot say that placing ignition smaller coils down inside, on top of a engines head, is in the long term more reliable. Heat degradation will be on the consumers pocket.
It does do away with travel distances, by a few nano seconds but the 18 gauge harness to each was a bean counters cash draw too.
Hopefully can the coils last as well? Scott Kilmer swaps them around and lets the scanner tell him again if it moved. He is yours and our kinda man!

Rethink and redo something, as this is the first side of getting things to burn correctly.
Even if it’s propane or ethanol, you got to get it in there.

The best made radio & microphones can sometimes be worthless like a thin string or tin can for a speaker.


Phil