I had a bit more time to play around with this, and updated my AMD chipset drivers, double checked that the RAM was in XMP1, still not seeing any difference.  The one last thing I think I'll try it to reapply the thermal paste between my CPU and cooler, it does seem to be running hot (the aforementioned CYYZ scenario has it around 70C), and when I was flying the Turbine Duke on a circuit around Ottawa last night the CPU was hitting around 80C.  Not sure if that's expected or not, or if there could be some temperature throttling happening.  

Also (and maybe conversely), on ChatGPT's advice, I ran the Cinebench multithread benchmark for the CPU and it came back around 17,300, which I'm told is within expected range for the 7800X3D so maybe I'm just chasing something that doesn't exist here...maybe this just is what it is at this point.  I might also look at a Cablemod replacement GPU cable to avoid any extra connections but I'm not really convinced that will make a difference at this point.

As long as the core clock frequency is held, there is absolutely NO need to think about temperatures except for the noise if the cooling solution is at its limits. Performance wise it doesnt matter if your 9800X3d runs with 5250MHz at 80°C or at only 65°C. 

The only thing you could check if you h.ve mistakenly set a temperature limit to e.g. 70°C only in your BIOS, but as mentioned, you would then see reduced clock frequecies...