Once again, thank you so much for the video. That's the most useful tool when troubleshoot anything like this.
That one looks like the correct behavior to me, though. The intercooler bypass has the power to melt components in the ducting system without any help from the combustion air heater. To quote the reciprocating engine Duke pilot the first time I delivered him my software to test, "Ok, make sure both of those are in before start so we don't kill ourselves." The reason the heating vent heats up faster and hotter than the plenum is because the plenum air is the source for the heater. The heater always has the ability to raise the temperature of the plenum air, so naturally, it will be hotter. I hope that one made sense? As far as I'm aware, everything is working correctly in that situation, but I will add this to my list to test next time I have the simulator open. I typically test many things at once, so this will be one of them :)