I am having the same exact issue, noise when letting off the gas, the noise is there no matter engine is cold or warm, and it stays at all RPM, but we can't hear it above 2K because of the engine sound (the normal sound LOL) and the road sound as well...
I took my car to the dealer many time regarding this issue, every time they told me its normal (as usual) the fourth time I insisted to do TSB 19-2140 and they proved, I just took my car 2 weeks ago and nothing changed at all, I think its something not related to the tensioner at all. I am sure there are many experts here and I hope someone help, what about the big power guys! how are they managing to add twin turbos and superchargers? what about people who built their engines, did they found a fix? are they still having this noise? even the 5.0 F150 18-19 having the same exact noise.
I tried 5w30, I tried 5w50, nothing changed the sound of this noise.
Is it a VCT solenoid? is it the butterfly inside the IMRC that is rattling? is it oil pump?
I am sure it has been found by someone..
Any help would be really appreciated
Please check the before and after TSB videos and the TSB.pdf as well
Enjoy the noise LOL
Any luck finding out what the problem is?