I have a 2021 Trailboss and it doesnt have AFM (fuel mananagement) and a non-ecotec 5.3L, but while browsing the Chevy website, it seems ALL the 5.3L engines are "ecotec" ? Am I missing something?
Doesn't the term "ecotect" just mean that it has AFM (active fuel management), eg. shutting off/on some cylinders as the load varies?

 

There were two 5.3L engines available in 2021.

The L82 with Active Fuel Management
The L84 with Dynamic Fuel Management System

They do the same thing (shut off cylinders)

Both are referred to as 'EcoTec3' engines.


https://gmauthority.com/blog/gm/gm-engines/l84/

 

You have the same engine (L82) that I have in my 2021 1500 work truck with a 5.3 Ecotec 3 engine. There was a chip shortage that year so some trucks that were made after a certain date did not get the active fuel management. Although the engine and everything else is exactly the same as one with AFM, it doesn't have the capability to activate it and GM has no plans to ever add a chip to ever make it work, which to most people is a good thing...lol.