This is quite a mystery. Based on your first post you did everything "by the book".
After removing the old spark plugs, looked OK, I squirted some oil into each cylinder and spun the motor with the starter button. (plugs out, nothing grounded). I'm talking just a few 2-3 quick stabs here, not a long crank. Would this have fried something? If so, why was I able to start the motor and run through a heat cycle to "burp" the radiator with seemingly no ill effects? Trouble didn't show up until the next day after washing.
WAG here. With the wires unplugged and not grounded the 50K volts (or whatever) is going to seek a ground. It may have burned a hole or found a crack through the insulation to ground. If the wires were dry then when the plugs were reinstalled the lowest resistance to ground was still through the plug so it ran fine. After washing the plug wires get wet maybe into the cracks or holes and with a damp insulator the wires are now shorting out somewhere instead of going through the plug. If you can fire it up at night or in a dark garage see if you can see any spurious sparks along the path of the spark plug wires. Also, I'd wipe down and clean the insulators with rubbing alcohol, let dry then coat with dielectric grease.
Used a cleaner and a gentle spray, not a high pressure wash.
Not using the high pressure wash is to avoid forcing water into the bearings (mostly) in the rear suspension. Swing arm, cushion lever, dog bone bearings are all unsealed and if you hit them with high pressure water it will force out the grease and rust the bearings. With a gentle spray you may have gotten an electrical component or wires wet that is causing the problem.
Should the secondary throttle plates be open at startup? Should they pretty much stay open? Looking at the linkages, it seems so.
The secondary throttle plates are controlled by the ECU. In prep-to-start (when the speedo needles sweep) the plates should open 100% then close 100% then open to about 10%. You can see this if you lift the tank so that would be a good thing to rule out. With the ignition key off see if you can manually move the secondary plates full open to full close to make sure nothing is binding, then turn on the ignition and see if they execute the prep-to-start sequence to rule this out as a problem.
I am going to try to clean the injectors better, and also get gas from a different station. I have a TPS on order. Won't hardly run at all now, and still no trouble codes.
I have some injectors from a K9 for sale in the For Sale forum, PM me if you are interested. If you decide to get them cleaned I have used RC Engineering