Little update.
After checking everything, the rig had aluminum cap and rotor, Belden High Temp wireset, plug gaps from .032 to .040.

So changed out alum cap and rotor with brass, replaced Belden wireset with new Belden's (didn't know how old they were.) and re-gapped plugs to .035.
We'll see how long that lasts.
Thanks for all the recommendations.