[Purdy Swoft]

Check the spark plug wire strips on the distributor. Some spark plugs are shorter than others and need longer plug wires. if the wires are too short and contact the distributor cap , the number three wire can burn through the cap and cross fire to the number four wire inside the cap. I had this problem. My car would run ok at low speed but miss at highere rpm. I happened to be looking under the hood one night with the engine running and saw the sparks flying between the edge of the cap body and the number 3 plug wire strip when I reved the engine. Check the distributor cap body for melted spots under where the wire is contacting the cap. this usually only happens if the plug wires are too short and touching the cap body. Just a thought.