Changed out my combination switch today. The problem with my old one appears to be in the slipring. My cruise control buttons won't work, or work intermittently. I've disassembled the slipring (A very simple device inside, I can't really see how anything could be wrong in there that would cause intermittent function, but I checked it all anyway.) Perhaps there's other problems with the contacts. I'll see about it, and go over the parts to find where the problem is later.
In the meantime, I'm very happy about having a properly functioning cruise control again. The turbo's cruise control seems to be more ... abrupt than the NA one. I wonder if it's a little gung-ho about engaging the vacuum pump, which would cause the throttle to open more suddenly. Or maybe it's just stiff and the cable needs to be lubricated. I'll try putting some graphite in there this weekend.
I've been collecting parts for the stereo system install, which makes me shake my head, since what I really want to do is finish the motor build so that I can swap it in. Or at least put the big turbo, AFM and injectors in the car.