Rats
My suspicion is (which is supported by Walters post) is that peak TIT is maybe 25 degF LOP EGT. I also suspect that the best economy line in the engine operators manual (do you want a pdf copy?) is maybe 25 degF LOP TIT (50degF LOP EGT).
Comparing the graphs of the different variant TSIO engines is pretty interesting. The best economy line is pretty much the same for all engines, but full rich varies quite a lot. I wonder if the best econ line is a proper engineering line (probably 1.05 lambda) but the full rich figure has some "political" element with less objective limits.
The CMI Operators manual says to lean to the fuel flow numbers, so I thought I'd try that and see what TIT I get.