Need some advice

Right, that is something I would honestly like to change aboot these planes.  Reading engine RPM would make so many things considerably easier for everyone using (and maintaining).

Things have been going much smoother since the pilots now focus more on speed than engine settings for standard cruise as stated in the POH which I believe was part of the issue, the accuracy of what the G1000 is reporting I will probably question for the rest of the systems existence as one plane just seems to need more rip 'ems and throttle to achieve what the other plane can with slightly lower settings.

From what I understand the detonation was caused by low power settings causing higher EGT (not monitored this is pure speculation based on input from someone who knows these things better than I do and even demonstrated them for me with their system where EGT is monitored).

When something didn't feel quite right our pilots default to Lycoming training and they put on the carb heat at those same cruise settings which probably further exacerbated the high EGT on an exhaust system that is well known for its questionable build quality overall with known back pressure issues.    A couple of valves were also recently replaced on a cylinder, and they showed signs of excessive heat as well but were only checked as the cylinder had lower compression compared to all the other cylinders and I suspected it had experienced detonation at some point though the lead build up covered the evidence on the piston head so the piston had to be changed as well.