Is it my coil?

1980 with Jimmy HS4s and Jeff 25D, electronic ignition, and coil 2 years ago. Car idles fine but when I am driving I am sure the tach actually jumped from 3000 to 3500 and I was not accelerating. Tach drops 500 or 1000 rpm for a split second and a few times the tach dropped to 0 for a split second. It seems to happen so quickly that it feels as if the engine has hardly slowed down.

Couple of times the tach dropped to 0 and the car did stall. I checked all my connections and when I wiggled the coil connections the RPM would drop and then resume. Coil connections appear to be tight.

Does this sound like I need to replace the coil?

From what you say about wiggling the wires I'd be inclined to check the wires are firmly attached to the connectors.

Firmly pull on the wire connectors in the ignition circuit. See if you can pull them off the wires. If you can, you found the problem, or at least one of the problems. I've heard a few complaints of the Pertronix wire terminal crimps not being good. That could be it? It could also be a failing engine/transmission ground strap. What coil are you running? If its the Pertronix epoxy coilI sent you, I really truly doubt that's the issue. Another thing to check is that you have a full 12V at the coil + terminal when the car is running! Less than 12V WILL cause problems!