Just a long term follow up...
Finally sourced another set of the iridium Pulstars, these aren't exactly like the first set, they are part#"BE1-iT" no idea what the difference is.
I wasn't able to pull the super lean cruise AFRs with either the "new" BE1-H (inconel/copper core electrode) Pulstars, or NGK iridiums, but I'm back at 20:1 with no evidence of lean misfire with the BE1-iTs, only swapping plugs and changing the AFR targets/adding the timing back in.
It even accelerates smoothly @20:1.
With the "normal" plugs, even 17:1 was having significant lean misfire, std LS2 coils, I need to make some mounts for the truck coils one of these days.
Its air cooled, and had a hard time staying >200F CLT when the outside temps are <80F when running that lean, so having proven it really WAS the plugs, I'll probably yank them back out and save them for next summer, as I switch to ~stoich AFR targets in winter to run at normal head temps. When its 100++F outside the head temp safety margin helps, also helps economy 3-4 MPG at cruise.
I actually need to hook the JAW WB serial setup back up so I can verify calibration when running that lean, seems to hit a wall at ~22:1 (the wideband, not the engine, it will still do 23:1 (indicated) with slight lean misfire) but 20:1 is smooth as 13:1.
I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...