UPDATE I just got a note from this 460 Ford problem
They took it to a Ford dealer this time, and they tested and found the ign module that was replaced before at another repair shop was defective. Ford tested other components, and didn't find any other problems.
They do believe that the problem is now fixed, but added that only time will tell. They were also very fortunate to get a refund not only for the defective
part, but also the labor to install it. They didn't get refunded for an hour's diagnostic time.
Thanks for all the replies that tried to help.
