Help me AEU86, you're my only hope

[jondee86]

Also I was looking at the way the AFR gauge behaves with the crankcase
breather blocked or venting to atmosphere.

Because of the much higher sensitivity of the narrow band sensor near
stoich, the gauge needle will always be much more active when he AFR is
near stoich. Conversely, when the mixture is very rich or very lean the
sensor is at the extreme end of its range and insensitive to small changes in
the mixture. In your case the needle moves further into the rich zone and
becomes steady which is in line with the mixture becoming richer when you
block the breather.

From what I read you should expect a narrow band gauge to have the
needle "twitching" as shown in your video with the crankcase breather NOT
blocked. That means that it is actually reacting to the minor changes in AFR
due to low V.E. and exhaust gas reversion that commonly occur at idle. My
wide band gauge always jumped around between 14:1 and 15:1 at idle.

That is what causes the unevenness you can hear in my video below. Bear
in mind this engine had cams so that exaggerated the rough idle.
https://i.imgur.com/JsnZvRJ.mp4

Cheers... jondee86