low power when hot?

Howdy!
Recently got my 72 Duster back on the road, and its been doing well for short jaunts around the block. Today, I tested it out for a slightly longer drive to a local car show (my first one and I was the only Mopar there). On the way back, towards the end of my drive, It was really low on power and not super responsive. I live on a decent size hill so I usually have to park it at the bottom and wait for it to be dead cold before I take it back up (which it does fine just off cold)

Idle is fine and it never cuts off unless its hard braking (I have just been left foot braking with the slightest bit of gas until I stop then it recovers fine)

my theory is its leaning out when the mixture gets warm/hot. but I want to gets some more input. Is this as simple as richening the mixture + a little higher idle? (currently 1.5-2ish turns out from seat)
Need more info on engine, general stuff.
If it stalls out upon braking or heavy turning it is too rich and choking out.
I know that does not sound right, trust me, read the spark plugs they will tell the story.