What your hearing is not lifters. The Duratec 6 has a timing chain pretensioner that uses oil pressure to take up the slack on the timing chain. In those few brief seconds until the oil pressure comes up the timing chain rattles on the cover. Most Duratec's do it. Don't worry too much about it. I have almost 100,000km on my car and it hasn't broken yet. If you want to try, you can ask the dealership to perform the TSB work, but they will have to keep your car overnight to witness the issue directly.
