Scott,
A little information on the layout of the Autorotor.
The snout is linked directly to the gearbox (it maintians the rotors relationship with each other) without any oil seals so it will leak oil if not used as a breather or sealed up.
The hole has a 1/4" BSP tapped thread in it.
If you read Corky Bell's book "Supercharged" it has photos of Autorotors with breathers attached. I followed the photos and did so. John C blocked his off.
By having the snout open to the atmoshere it allowed the vacuum in the manifold to draw the oil out of the gearbox and into the rotors. From there into the engine was a short trip.
The fix is to have a 5thou air gap on the throttle blade and block the hole off. This stops the sharp vacuum when the throttle snaps shut.
I think a smarter fix is to have a very small bleed into the manifold after the t/b that runs bach to the air filter. This would mean if you (or someone else) inadvertantly adjusted the throttle plate and closed up the air gap you would still have the air gap.
I think a small 1/8 hose from one side of the throttle to the other would most likely do the job. You could experiment to see what the largest port size you could run but still allow the ISCV to do its job. I'll probably start with a 1/4" hose and see how it goes and keep reducing it until it will idle.