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Totally agree after breaking in my pa32. 300.  My archer O360. And now my lance to breakin eng must be run 75% or greater and leave mix up no leaning to keep proper cooling and watch cht’s.  First 25 hrs are critical to avoid cylinder glazing.   U will find ur eng burns more due to eng putting out more power.  From prior to rebuild.   Reason ur cht’s run cooler for lean of peak is the cylinders switch from fuel cooling rich side of peak to air cooling lean side of peak.  Egt’s are going to read high because of the exhaust is exhaust.  Remember the egt temp is relative and to be used as a reference to change, not a limit.  CHT is a limit and to be used to protect ur cylinders.  Much more important.  During breakin u will first see high cht 400 maybe more not to exceed the 450 limit.  As breakin happens within 10 hrs the temps should start coming down below 400 degrees. If u have a cylinder that remains high it still not broke in.  Number 3 and 4 due to location will usually run 20 degrees warmer.  5 and 6 will be cooler .  Egt temps can vary between same engines because of installing location of probes. Manuals call for jpi ei. To place 4” to 1”. On each cylinder .  Depending on curves ,welds , etc they could be 1/2 to 1 “. Different.  Only egt temp is to note on full power take off.  And then use that number to set mix for high density airport prior to take off. Should be 1250 to 1350.