Saw this old thread pop up, and just got my jeep back today from the dealership.
My jeep is a 2016 and has about 54,000 miles on it, and you could say it is heavily modified, after the transfer case, everything is different, axle housings modified, different axle shafts, drive shafts, steering knuckles, steering linkages, steering gear, etc. I was legitimately worried about warranty denial, because of the extensive mods.
What was done on mine was new rocker arms on the side of the number 4 cylinder, new tappets, and new cams. Also associated gaskets, etc. They tech billed out 3 hours for it.
As far as I can tell there are a couple of things. Immediately, mileage when up, according to the computer, and of course, they are absolutely reliable.
Also, the ticking that has been going on forever, without a code, also stopped. We will see if both things continue,