What's the name of the temperature sensor closest to the PCIe slots in a MacPro5,1?
This is the full list - from iStat Menus  



There isn't really one anywhere near the PCI slots that's also in the same compartment. 
CPU, DIMM &amp; IOH are all in the lower compartment, Drive Bays &amp; PS are in the upper. 

I've seen machines reporting a temperature for PCI Slot 1 - but these may have the original graphics cards in them... mine barely has an original anything.