Pulling plug #3 has almost no effect on how the engine runs. Hmm!
In other news, twiddling the idle air screws on the carburetor has much more effect on the driver side (cylinders 4-6) than on the passenger side (1-3). I can back the idle air screw out *WAY* more on 1-3 before the idle starts to get worse.
Also, I managed to burn 1/4 tank of gas on a ~50-mile drive.
Methinks I may have a vacuum leak ...