Really sorry to hear. For those that don't know, JE is one of the sharpest guys around when it comes to the 5.4, period. He does his own work and knows more than I ever will.....take his word as bank.
Some of you guys know that I build two stroke engines.....very atypical two strokes....they run hard and last! LOL
We all have been reading or experiencing these valve train failures for years. I will add my 2 cents. I never had a prob with either my '99 or the '03 with any part of the valve train..... around 223K and 165K on each respectively. I also haven't had any issues on my 3.5 in 133K.
My feeling was always from the timings, that the 5.4 in its various renditions was a torque-monster and did not like being rev'ed, AT ALL. I never ran either hard. I have a garage full of 140mph machines, I didn't need to dog an old truck.
My 3.5 is a different animal....it loves to rev of course with it's twin turbo's, if built right, could be a blast....BUT it also lacks in some of the same areas as the 5.4 before it. I do not run my 3.5 hard either.........fwiw.
Does it suck having a machine that I cannot take to its limit.....depends how you look at it.......not running them softly might BE their limit! lol
jeff