Thank you for the inputs guys.
The intake leak seems to make sense and will check everything is tight - I did replace the gaskets last year as part of my annual.
It seems strange that this condition common for both 1&2 and seems to have been impacted/exaggerated by me blocking the airflow to the front two cylinders. - it is hard to see but the RED EGT#1 is hidden below the YELLOW EGT#2 in this graph. For example at time 1:00 EGTs are 1:764, 2:771, 3:950, 4:939, 5:1008, 6:942 - 1&2 are a 200F below everything else. the same temp differential seems to exist at each power reduction downward spike. Of note the CHTs for those cylinders remained the highest of the six during those spikes.
Below is the overlay with the MAP.
To explain a few of the spikes I will give you the thumb nail debrief.
I leaned at time 12 minutes or so. Did a stall at time 26 minute - to check the impact of my new dams on CHT temp - then flew an RNAV from 6K descending to 330ft beginning at time 57 or so - mixture goes to full rich at time ~ 1hr as part of the landing check. Then it was a couple of T&G in the Charlie, then back to my own little airport for the break and a few landings. I leaned during the RTB at time ~1:10 then go full rich at ~1:24 or so as part of the landing checklist - I then lean at ~1:37 for taxi.
I am not stressing this but am curious.