OK, I got the scoop. The kit was associated with an interesting (and apparently tense) little chapter in Subaru history.
It seems that several variations of the Hitachi carburetor used from '77-79 exhibited a little problem with sustained high speed driving at temperatures below about 28 degrees. The problem was that the throttle plate would stick open, causing a very unnerving "cruise control from hell" effect!
The problem was mostly reported in 2wd MT vehicles where a cold enough air blast into the engine compartment was capable of cooling the carburetor enough to cause the problem. Apparently some runs of carbs had close enough tolerances for the problem to happen, but most did not.
Having experienced the problem himself, my brother said it's really scary when the throttle sticks open at 75 MPH with a tight curve coming up! The reflex of depressing the clutch was also an interesting experience!
Apparently, the only part that's really needed is the plastic shield. The other parts were designed to help, but he felt they were mostly put in the kit to help with appearances and impressions of the "lawyer" kind. Not known how many accidents resulted from this, but somehow a recall was avoided. The kit was sent out as needed (mostly to Northeastern and Rocky Mt. areas).
My brother worked in the warranty dept. for Subaru South through '83. He knows about that cold weather kit because I remember him talking about it many years ago. He knows a bunch of other stuff like that from the same time period (and has a memory like an elephant). I'll call and ask him tomorrow to see what he still remembers...
