Never-ending tale of woe F-150

I have the same issue again. Was told by the dealer it is a common issue with the 5.4L but they didn't explain why. I had the passenger side done at 61K miles two summers ago and it just started up again, can't tell which side but guessing drivers. The first was done under the Extended warranty I purchased from Ford and this one will be covered as well since I just turned over 90K miles. Just got back from a 3 month trip through Utah, Wyoming, Colorado and New Mexico and the truck peformed flawlessly as usual. It still runs and pulls like new. Oh well, back to the dealer. After this repair I will about break even on purchasing the warranty. We just bought a car so the final 9K warranty miles will be mostly towing.