I read Mike Busch's article and it disturbed me because my IO-360 Angle Valve engine typically runs with 260--290 CHTs. Mike's claim is that the lead scavenging is less effective.
Funny though, we used to run auto engines with fuel with about the same lead content (not the spec, the actual content) and CHT around 190F. I used to overhaul Volvo B-18 and B-20 engines and the degree of lead deposit throughout the engine could be correlated with oil type and change interval. Paraffin-based oils seemed to be less able to hold lead in suspension than Asphalt-based oils. But I never ever had a sticky valve on a auto engine.
I do run TCP in my IO-360, although not religiously. I have been planning a cowl mod that will increase my CHTs, primarily motivated by aerodynamics, not specifically to raise CHTs. In the mean time, I am happy to read opinions here that counter what Mike Busch said. Hope you guys are right.
Seems like with lower CHT, there is more heat flux off the valve through the guides into the head, so the valve stem should be cooler, and have less coking/oxidizing of the oil.