68 Valiant dies and runs lumpy, then suddenly runs fine.

You should not pull spark plug wires off, and ESPECIALLY not with more modern electronic ignition.

A better way is to wiggle the dist. boots up, and use a small grounded probe to work down beside the wires one at a time and ground them out.

Pulling wires can cause crossfire which leads to false conclusions, and can damage electronic modules

This sound to me more like "dirt in the needles and seats.", vacuum leak, or vapor lock


Throttle shaft? These can actually be pretty bad before they run that bad, and typically show up in heavy trucks with governor carbs, because there is so much dirt, force, and "trauma" on the shaft.