That makes sense. Now the odd thing. I checked all of my vacuum tubes this morning and didn't think that I had found any obvous leaks. Put everything back together, started it up, and presto-- no rough idle and the cruise control worked perfectly all day. I don't really feel like I fixed anything, so I have a sneaking suspicion that it is going to come back. At least now I have a better reason to more thoroughly rule out a leak with wd-40.