JIM, and vanageeks...
: '84 right?
................. YEP...

 Probably has a microswitch or two where the throttle cable
: attaches to the throttle body.
.......................It was sticking last season, I cleaned it
with  electronic cleaner, and it completely degunked it....

Make sure that the wires are hooked up.
......................DI-electric silicone on contacts.

: A faulty "full throttle" switch (the one that activates when
the
: throttle is wide open.) will do just as you have described.
Sudden!
: drop of mileage.  Ask me how I know.  BTW, if the switch has
failed,
: find a boneyard one.  New they're about $50.  Used... about a
buck.

: