Okay. It is a cleaning question and a grounds question but here's the problem:

Check engine light that is going to keep it from passing smog check. OBD codes 1-1-3 & now it 2-3-2.

And here's some of what hasn't fixed it:

I am ready to put the original ECU 556 goldenrod back in; not sure which one I put in that tested okay and has been good for a couple years. I've troubleshooted my own, my wife's, and my 5 daughters various B230Fs and swapped loads of parts over the years and the original is a known good one that I want to clean-up before I install it because it's been unused for quite some time. Ditto for the AMM if necessary.

It has a brand new 02 sensor, flame trap & hose, air cleaner, irridium plugs, a hefty dose of Techron Fuel Injector cleaner; plus, fairly new cat converter & AMM accordian hose and, yes, I'm fairly focused on it being the ECU. I had to repair some wiring due to rodents. But just in case I've ordered a new ECT sensor. If I remove the battery cable and it is cold outside it has produced various patterns of idling symptoms; including, running strong & smooth and no check engine light for hours.

So... got any hot tips for cleaning vital contacts and locating the pertinent grounds?