'09 5.4 with ~180k on it. Runs fine, no real issues with the truck (hope I haven't jinxed myself...)

It does have an odd exhaust smell. Don't recall at the moment if it's all the time, or just for a period after start-up. I'll monitor that as it may help in diagnosing.

It's not a burning smell, or not like unburned fuel. Just a very pungent, strong smell.
Not sure how else to describe it.

I realize this is somewhat of a shot in the dark, but any indications where to start looking, what may be causing it?

 

Catalytic converters are a consumable item and so are O2 sensors.

I would first change all O2 sensors. Monitor the odor then move to consider installing new cats.

Personally, I would change the O2 sensors, then wait for a code like a P0420 to pop up to install new cats.

 

I had suspected it might be the/a CAT but was looking for some validation.

For now, believe I'm pretty much in-line with your thoughts. Guess I'll just live with the "smell" until it's absolutely necessary to change parts.

Appreciate the reply.

 

You might want to throw some cat cleaner in the gas.

 

Check the fuel mix. It may be running rich and if so, the exhaust will smell like acid.

 

That stuff really work or is it snake oil?

 

https://mechanicbase.com/reviews/best-catalytic-converter-cleaner/

https://theautomotivedude.com/catalytic-converter/catalytic-converter-cleaner/

Worth a try.