Corvette: so small a thing
So the car suddenly started running rough on a cold start and staying ragged until it warmed up. Once warmed up, it ran fine.
A quick look under the hood revealed a little silver weight sitting on top of the intake manifold. Turns out, that little silver weight is part of the fast idle cam, which in turn is part of the automatic choke system that lets the car start smoothly when cold. (For a full explanation of automatic chokes and how they work, see this article at Hemmings.)
Well, it turns out this little plastic part (why plastic, Chevrolet? why?) runs less than $10. Of course, taking apart the Holley carb assembly to replace it required the touch of an expert, so after a quick trip to C2 Corvette expert, Pat Hendrix, at Precision Motive, everything was back to normal. Cost of repair = $100.