This is why we do runups

Jim,

Yes, but that statement should be further qualified by saying that descents
should be made at less than 75% power or else EGT and CHT could exceed
operating limits. 65% power sounds like a good number. Some carbed engines
with good fuel distribution will run smooth when too lean (close to peak,
either rich or lean of peak).

Actually, that doesn't make sense. I think you may mean
"inappropriately" lean, rather than too lean. The worst spot is about
50 degrees rich of peak when at high power as that is generally max
for CHT and BMEP. So long as you are richer or leaner than that, you
aren't going to hurt the engine. Leaner is generally better in terms
of keeping temps down and plugs from fouling, so long as the engine
runs smoothly.

All the best,
Rick