Have you checked your fuel pressure? To function properly the engine needs a constant supply fuel at the correct pressure. Get a Fuel Pressure Pressure Gauge and attach it to your valve on the passengers side in the rear on the fuel rail. To see what the fuel pressure is doing at speed, just tape the gauge to the windshield and see what happens. From there verify that your fuel pressure is within the limits set for it by GM. If they are not replace your fuel filter first and then verify that your fuel pump is working properly. On my 1988 Coupe the fuel line corroded closed internally, fuel got through but not in sufficient quantity. I ended up installing a new fuel "supply line" as my "return line" was still open and flowing just fine.
I have also seen loose power connectors at the side of the distributor cause the power to turn on and off by itself which could do what you are describing. Make sure that your engine is grounded properly, a lot of problems with C4's is caused by faulty ground straps. I fixed the ground strap that connected to my exhaust to the frame and all the sudden the power antenna started working properly. It had 12 Vdc but not a good ground connection which is all it takes to start problems.
I am a big believer of BG 44K Fuel System Cleaner, if I were in your shoes I would try that first with some good gasoline. BG 44K is not a "Snake oil" and I have been using it without issues for over twenty-five years. Then you can start pulling spark plugs and checking wires. To check the spark plug wires it is easy as all you do is wait until it is dark and open the hood. If you have any bad wires you might be able to see them shorting to ground on their way to the spark plug. If you see sparks buy new wires while you are at it. Spark plug Wires usually last about ten years at most. Spark plugs are a pain in the butt but they should be replaced every so often as well. My Corvettes don't see many miles so I probably waste spark plugs replacing them before they wear out.
This should give you a good starting point! I wish you the very best in sorting out this miss you are having. In the old days I would have done the points and plugs first as that was the standard way to solve a intermittent miss like you are having. Today with the C4's I would bet the problem is somehow related to the fuel injection system.
Be sure to tell us what finally eliminates your miss! We all need to learn all we can so we can help others!
