my 1978 ols bravada misses out when it wet outside
we changed coil cap plugs and plug wires with no luck the missing keeps getting worse when its dry out it seem to run fine ?
If you open the hood at dusk when it's damp out, you might see it arcing... I used to spray my cap and wires with a plastic like product called "Wire Dry". I would remove the cap with the wires attached, hang it up and spray everything (be sure to write down where the wires go first). After it dried, I would reinstall and give it another coat. It worked good on my rally cars and kept them firing through the water crossings.
there is a weather seal where that seals between the area in front of the cowling to the hood. If moisture gets between there you can have these problems.