Well, I'm thoroughly confused - when my wife got home, I asked her how the car had been shifting since I'd been gone. She told me she hadn't driven the Merc all week long, but did take it to work this morning, and didn't seem to notice any rough shifting. I took it for a drive, after I'd readjusted the vacuum lines as noted in my last post, and it was back to buttery-smooth, unobtrusive shifts. So I have no idea if I fixed it, or if the car somehow fixed itself (I know, makes no sense, but based on my wife's report...?).

So anyway, things seem to be back to normal, for now. I'm still planning on picking up the Mityvac and giving the whole system a once-over, but I'm really more confused than I was before I started. If anyone can make any sense of the pics I posted before, I'd certainly appreciate any insight. I've tried deciphering the engine's vacuum schematic, but it's pretty indecipherable to me at this point. For now, I'm just going to cross my fingers and hope for the best. Plans to overhaul the vacuum system remain on the short-list, though.