I just heard from a friend who's an engine rebuilder and he says that the 5.4's have a high failure rate after about 100K miles. It seems the long cam chains tend to stretch more than normal over time and wear out tensioners and guides, not to mention jumping a tooth occasionaly.
He also says replacement parts are extremely expensive bringing a complete rebuild up to about $4500 in some cases.

Any experiences from high mileage 5.4 owners?

 

HI!... Well I have about 108,000KMS on my 5.4 and have never had problems with my timining chains. The last time I had my had gaskets done the mechanic checked for me and said they were still in NEW like condition. I'm not worried.