How hard is it to get scope probes at the CPS input ports at the ignition module?

Perhaps the CPS connector is the problem, It couldn't go open without
killing the engine dead, but what happens with resistive contacts?
Would the old sensor have worked by just unplugging and plugging back in?
I wish I tried that first.

My car suddenly went into "limp home" or "The governor mode" was turned on.
(maybe they are one and the same?) Have you measured the CPS signal at the
module with the car running? Is that line free of random hash that might
give the wrong RPM value to the module, and start governor mode?
Do the modules have any filter caps that may be out of limits with age?

I found no ground connection from the metal bolthole insert of the sensor to the ground lead of the harness, so the CPS harness shield isn't grounded at the transmisssion. Is that normal?

How about the main connectors for the fuel and ignition modules, do they
get finnaky and need attention to end these kind of chronic intermittent problems?

Cheers, Bill