I had a missing problem at high rpms and did a lot of research. I found a lot of Ford TFI failures. There was a class action lawsuit that cost Ford Millions of dollars in Ca.
Ford mounted the TFI on their 80's - 90's model cars / trucks on the distributor as a heat sink. The problem was to much heat from the motor transferred to the TFI causing failure.
They moved the TFI to the fender (other places on different vehicle) and mounted it on a aluminum finned heat sink.
I found a small Ford in a junk yard with one and installed it on my Cobra. You have to cut part of the fins out because of the different's in the TFIs.
I had to extend the four wires from the distributor location to the firewall where I mounted my new heat sink.
So far so good.
Dwight
One of the many links I found when I Google Ford TFI failure.
Ford TFI Ignition Control Modules - FSB Forums