All good suggestions. The high voltage module is new, as is all the wiring, including that long lead to the bottom of the distributor. I will check and clean all connections again. I changed the air filter (dirty) and replaced a vacuum line that was cracked. I also shut off the hot air intake that enters the air filter basket. Couldn't tell if it opens and closes properly. It seems to be running better - idling more smoothly and not knocking and stumbling on acceleration. Then again, I have been there before also. Thanks to everyone for the suggestions. As Sherlock Holmes believed, eliminate every possibility until only one is left. That will be the solution, no matter how unlikely it may seem.