I have a 2022 7.3 on order and have been wondering about how smooth it is at idle. The 2016 5.0 I have now is the smoothest running engine I've owned. I can't even tell it's running when sitting at red lights. The 5.4 I had previous was definitely not as smooth as the 5.0.

 

The 7.3 is a lot more engine but still a relatively quiet engine.
It's the cabs that make a difference, these newer trucks are extremely quiet inside.

 

Our new 7.3 is quieter than than our 2018 6.2 was. It is extremely smooth at speed. Once in a while, you can tell there are a lot of cubic inches at idle. In general, our 2021 Lariat is quieter than our 2018 Lariat was. (Rides better too)