Well, that explains your odd MAP data. I cannot tell if that head has been overheated, and it does not appear to have run lean recently, but that shouldn't be an immediate problem anyway. What I know of seat issues centers simply on that seats drop when the seat is smaller than the rabbet/recess it is squeezed-into. This is more common when there is overall chamber and head overheating than lean run, because lean exhaust heats the seat quicker, which just makes it fit tighter - though in some cases it can expand the rabbet and loosen the press-fit upon exhaust and seat cooling or do it after many cycles. Long-term lean can lead to overall head overheat just like any overload, and though this isn't a rule - it should be relatively balanced assuming the seat remains similar or hotter than the head. Maintaining proper ignition timing is important whether running rich or lean in order to help avoid overheating, seat cutting or erosion, etc. Running too rich can lead to erosion, pitting, and valve recession or "sinking seats".
Head overheat may expand the head more than the seat, which is generally related to poor head cooling (e.g., poor airflow), insufficient heat dissipation (e.g., excess paint, corrosion, bugs, etc), or excess generated heat or power for the existing cooling capacity. An example of the last case is VW Type 1 engines that are limited to around 90hp continuous, as they simply cannot shed more heat at higher sustained
power levels. Of course, this assumes the head was machined properly for the press-fit seats, and there is no other damage such as cracks that can reduce the press-fit holding it in, or other valve train issues such as weak or broken springs or valve bounce causing "seat pound-out". I can't go into every case scenario or how some effects tie into others, but I hope that helps.