Sorry, time for my annual summer whine (5 years and counting) about high CHT on #2. (IO-360A1A, 1970 M20F)
Yes, the silicone baffling has been replaced and all the metal baffles are in good shape and properly installed (first year attempt at a fix!)
Yes, I've swapped CHT probes...NOT the probe.
So, here's the bizarre part, #2 runs hot at full power (when OAT is > 95F I have to back off power to keep #2 under 400F), yet when I get to cruise and pull mixture to LOP, #2 is the LAST cylinder to peak! That is, it seems lean at full power, but appears the richest cylinder when at cruise (22" and 2400 rpm). I don't see how it can be an intake leak as at full power the 'leak' would not be noticeable, whereas at reduced power the leak would manifest as a lean condition, but the mixture pull to LOP refutes that!
And, in cruise, it runs about 40F hotter than the other three: 360F vs. 320F
Incantations, voodoo, wild theories, all welcome!