Chasing this cooling issue for months

One regular question is "how do you know the temperature sensor is correct?". You are thinking of this since you compare to your engine performance. I assume you are using the small factory sensor screwed into the front of the intake manifold (1/8 NPT thread). If so, I doubt that more external air flow around it would change the reading. I think those are a resistive thermometer (RTD) which is usually a spool of fine platinum wire (maybe something cheaper in automotive). If it was a thermocouple, there are many strange false readings possible from connectors and such, but I don't think they were ever used for coolant sensors. If you have some other after-market or home brewed sensor then air flow might affect it.

Assuming the sensor reads correctly, you might research the "bypass hose" and flow circuit from the water pump to the intake manifold. I assume it is named that because it bypasses the thermostat. Maybe there is supposed to be a flow restriction washer or such somewhere. I have never studied it.