The new Coyote's have 16 injectors, 8 snappy DI ones, multiple fuel pumps, cam phasers, timing chains with guides and sliders, valve train noises, oil pump action, pistons slipping and slapping, intake noise, exhaust music, accessory noises; like alternators, water pumps, AC clutches, Electric steering motors, fans, etc etc.
And a partridge in a pear tree...
I have to say I was expecting something when I got the '19, but a couple of folks don't hear the same thing. And the Mustang GTs have the big engine cover to damp out sounds too. I would say that if it was a continuous noise, I would probably be irritated by it.
If the OP is truly experiencing piston slap, then it's definitely something to identified by the dealership.Thanks for sharing your expertise, Pat. It's much appreciated.