I just replaced my plugs with the FSM recommended Denso's (W16EXR-U), as my previous set were in my motor during the head gasket leak (they only had 1500 miles anyway but you could tell there was an internal coolant leak). And I've only got about 500 miles on these plugs on the new engine. I will check sometime this weekend or next.

Flashes across all spark plug wires with the timing light are consistent across ports. They are OEM Sumitomo's, with about 3k miles on them so I don't see an issue with plugs or wires at this point. Cap and rotor are 3k old OEM's as well with new o-rings. I'm still thinking it could be the physical distributor given the timing light/mark jumping around, which is messing with the Ne signal (see below about the ECU resistance test failure on that signal to E1). Especially since the Ne is sending the RPM signals back to the ECU to calculate A/F ratio. But still ... why does this only happen in closed loop and not in warming up when I get no misses at a slightly higher RPM (~1200 RPM)? I was under the impression that Ign and Igf signals are only used in the first few seconds of starting until the ECU can get a good Ne signal direct from the distributor via the ignitor for RPM's. Unless Ne is ignored until it's warmed up and goes into closed loop, but I think that's a false statement from what I've read. Again, distributor is probably a "throw a part at it" attempt at this point.

o2 sensor update: I tested again to get the learned Vf signal from the ECU after driving around for 30 minutes this morning and I see 0.43. Since my active oscillations were between 0.065 and 0.85, this seems to fall just above the midrange (57% in the range) which according to some Vf documentation should be perfect with a 2%-3% error correction bringing it back toward the exact middle of that range. I can't seem to find a way to test the o2 sensor to get the 1V to 5V ranges per the FSM as it requires some SST on the large connector. But I'm assuming I would see a similar set of readings for the oscillations and learned value, just on a different scale.

Vacuum Measurement: I decided early this morning to pick up a vacuum gauge just to check there. Plugged into the P/S port on the plenum and got 20 Hg. While the misfires happen, it would waver a bit, but nothing beyond a fraction of Hg. I think 20 might be a tad high (most posts I've seen are 18-19), but it's not low, which would indicate a vacuum leak somewhere. It's also a cheap Harbor Freight gauge so I'm taking 20 to be 18-19 ...

Another thought I had about the "age" question. I have a spare ECU coming in and I will be tossing that in there. Theory here is, it's good to have a spare as the original is going on 35 years old. And, unfortunately, there are countless "misfire 22RE" threads across the Internet where after 10 pages of troubleshooting, someone says "I swapped ECU's, it's fixed." and that's the end of it. It's like resetting the home router or cable box by rebooting it type of effort, but I've always wanted a good spare should something ever happen to mine.

I still want to investigate the Ne -> E1 open resistance I am getting. FSM says 0.14 - 0.18 k-Ohms. I forgot to slice open the plastic which encases the 3 wires (including Ne) from the ignitor connector back to the main harness in the plenum/intake when I was resoldering/wiring all the FI connections last weekend, and just lazily checked continuity which was fine. Still haven't found an answer as to whether that reading matters or not. 1 or 2 threads out there with people with a rough idle, saying they also had open resistance there on that check, but no follow-ups or answers as to whether it matters. I don't want to dig into that harness again unless I can get an answer as to whether it's worth it. By all means, yell at me if I shouldn't be ignoring this I'll happily run a brand new wire all the way from the ignitor connector's Ne all the way to the ECU. I'm just not wild about trying to remove pins from these various connectors, as I haven't found a good writeup on how to do it yet and would hate to break these brittle plastic connectors.

I won't have any updates for the next few days as I'm waiting on parts to do the following repairs/troubleshooting:
- New distributor
- Denso fuel pump and associated hardware
- EFI Solenoid (issue below)

The EFI solenoid is another one like the Ne -> E1 which I'm not sure is causing a problem, even though it's failing the test. FSM says 2 - 3 Ohms. I'm consistently getting 3.3 Ohms on mine. Is this really bad at just 0.3 Ohms out of spec? No idea. Stethoscope on all injectors has them firing at warm idle without problem. But a used one wasn't that expensive, so just awaiting that to swap it in/test the Ohms. Input here from folks would be nice.

That's really all I have left to try at this point. Grounds have been checked, cleaned, more times than I can count. I may go through and super clean all the connectors related to EFI with contact cleaner again as well.