Unusual pinging issue (2005 Ford three valve V10)

Mike, if that gremlin comes back to haunt you, I wold consider trying something you maybe already have.

On my previous Ford, I ran into an issue where some scanners, like the one at ORilley's would say all was well even when there was a light on on the dash - but that was an electrical issue.

I would consider tossing the money at it and have a Ford scanner hooked up to it for diagnosis. my first problem there would be to first find a competent diagnostician.