I think I may have found a new failure mode in our cars. (Unless someone else has ran into this, but I never saw a post about it).

Symptom: At idle, dash backlights seem to "waver" in intensity. It's a gentle oscillation that runs about 2-3 cycles per second, a DMM can't follow this and essentially averages, showing little or no variation.
Because the DMM didnt see it, I really thought it was a variation only happening is certain instrument panel circuits. I should have known better, as it went away above 1500rpm.

So, I really thought that, at worst, it was the alternator not keeping up with load (tho no reason it shouldn't, no one else reports this symptom). I sure have a lot of alternator issues with this car.

While working on my new "battery drain" paper, I got to messing with my battery cables and realized I'd never put the redundant ground in THIS car I had in the Graphite. So, yesterday, I did just that, just on general principles, I put a #4 cable from the bolt James used to the battery negative cable. SUPER easy 'fix'.

Well........................
Today, running around in the car I noticed that the instrument panel pulsing is gone.

I have said it before and I will say it again: This "round robin" ground from block to chassis to battery post is asinine. EVERY other vehicle I have owned had:
A HUGE 2 or 4 gauge battery ground cable to the block.
A smaller, number 10 (or so) wire from battery ground post to chassis.

I've had a LOT of issues with the SE - almost all have been STRANGE electrical issues. This was a cheap, easy fix to one of them - and I wasn't even trying to fix anything, just doing what I think should be done anyway.