Just a thought about defective Ford engines.... Back in 88 I bought a new 88 Stang GT and was lurking around the garage at the dealer while the papers and such were being drawn up. There was a row of 10 5.0 V8 engines. Not the HO version just the std V8. I asked the service manager and he said there was a lot of bad engines that had been installed and they were there to replace the defective units. He didn't care to comment on what the issue was either. I'm thinking that must have been one heck of a defective lot being there were 10 just in this dealership.
Hope your problem is something much less and good luck. G.