Well, I had a wiggle around this evening and found nothing seemed to cut actuation of the solenoid during the solenoid output test, short of unplugging it. Didn't bother recording much of that. It was me poking and prodding around the wires that go to the sensor and kombi valve, with no change throughout the test.
Checked voltage on the two wires going to the kombi valve: 12.3#V on one wire, 2.5#V on the other. Not sure if the other wire should be at ground, or not. I didn't check to see if that 2.5#V drops to zero upon actuation - that might make sense?
In any rate, I'm not sure where to go from here. I manually actuated the SAI pump relay in the fuse box, and also through the output test, and there seemed to be no change in operation there. If I monitor the sensor values when actuating the pump via the relay, they climb from the 14.4# to 18#, but I was not able to also monitor the change in pressure when the kombi valve actuates.
At this point, maybe I'd be wise to get ahold of my mate's MK7.5 GTI, and see if his kombi valve is also at 12.3/2.5V at the pigtail.
I'm going to remain hands-off for the next week, and let the car figure out if it wants to throw a code again. For all three cold starts today, I did not see the SAI system running through OBDEleven. I went out at lunch and also monitored the same sensors on my coworker's MK7.5 GTI, and his system ran as I would have expected.
One last thought before I sign off - 'Exhaust temperature 1 bank 1' is the sensor to poll instead of the pre-cat temp. I saw a difference of 550degF between my non-op system, and coworker's operational system today. Barring being able to fix the blasted system, I wonder if there's a value that can be adjusted to allow a lower temperature to meet the threshold.
Sorry for the wall of text, by the way. I am admittedly enjoying trying to narrow down the cause and solution to this issue, and it's nice to be able to converse with others who've experienced a similar issue.