Del, a question for you.

It could even be the new plug wires Rob.
Are they stock suppressor style or some "performance" style?
One easy thing to do that could also make a difference is a condenser connected into the power supply side of the coil.
You can temporarily connect the condenser to the positive terminal on the coil, then ground the canister end anywhere you can and see if that clears it up.

This was the old school way of dampening ignition noise with most points ignitions.