My rattle issue is finally over. My truck went to the dealer 3 times. I have 54,500 miles.
My original rattle was the chain. I would hear it after the truck sat 2+ days.
My first visit they did TSB 16-0027. It was there a few days shy of 4 weeks. About a week was wasted with them trying to hear the noise. 24 hours after getting home from the dealer I heard a rattle on startup. This time I would hear a rattle after the truck sat for 12-24 hours, but not after it sat about 36 hours. I checked my receipt against TSB 16-0027 and they replaced everything listed on the TSB.
My second visit they wasted a few days listening for the rattle. They had another Ecoboost that they completed TSB 16-0027 on. It also had a rattle after the TSB and they replaced the main chain tensioner on it. They guessed that the tensioner would fix mine too. It did not.
My third visit I dropped the truck off one evening. I went back 24 hours later and started the truck for the tech and service advisor. They both heard that rattle and stated that it was pretty loud. The tech immediately said that it was a phaser clacking. They had my truck about 2 weeks. This time I was given a loaner. They replaced both exhaust phasers (again). I have not heard a rattle since.
Mine would have been repaired the first time had it not been for a bad phaser. Everything was covered under warranty.
I also have codes P054A and P054C. Timing advance on cold start up. From what I have figured out, the codes are permanent codes because they are considered emmision codes. They technically should clear themselves after a while, but after about 1,000 miles they have not. I will be dropping the truck back off this week for the codes and rear end howling.
@rbrown