The impossible to solve overheating problem

As long as we're beating a dead horse. :-) FWIW, a laser temp gun helped me determine air flow problems. A thermal imager would be useful also. In my case at idle, air was being sucked out from under the hood past the front of the radiator and back through again. I basically overcame the issue with two spal hd fans with sealed shroud and a radiator flap/gasket. Then I created a new problem of blowing out a ton of hot air - needing air cleaner ducting to avoid sucking in the hot air. Looking at the OP pic, that's going to be a problem there - at idle, that wide open cleaner is sucking in some nice hot air from the exhaust headers and if the radiator/pump/fan are doing their job. I'm confused a bit by the low-speed heat issue but that could just be low rpm coolant flow. Or else, the OP has issues unrelated to cooling - and something like blow-by, etc.