Here's the deal;
Air entering the intake from under the throttle blades will not cause a runaway............ wait for it............................... because there is no fuel in it!
That's where I was confused initially, but apparently a low vacuum condition can cause the carb to "add" fuel into the venturi because it acts like it's under a load, or so I've seen/read. Sounds odd but it can apparently happen with these. I'm just not sure it's going to cause a run-away this severe.
