I haven't done a lot of egt testing on piston motors, but for rotary, I use 02 for the setting of the fuel map, I use EGT for the timing map along with the dyno torque reading, we only have 2 exhaust ports to check on a 2 rotor so its easy . Once I have the engine making the power I think the combination should make, I then check the egt's to make sure they are in the zone, if too hot, I bring the a/f's richer to control the egt.
A lot of people just tune for maximum best torque and then start melting things.