There can be several reasons for your PV to be set at 160F and over-running to 163F.
1. If the set display is at 160F and the actual display is at 163F then there is something wrong with the PV.
2. If the set display is at 160F and the temperature reaches 163F then starts dropping back down then you are monitoring the temperature at the wrong point, like at the RIMS inlet. Everyone forgets that when the RIMS heater turns on the temperature change is not instant, it takes time for the higher temperature to travel all the way through the mash tun. This is exact why you should monitor the temperature at the outlet of your RIMS tube. I have mine even closer - it's at the top of my RIMS tube.
3. If your PV is set to 160F and the temperature measured by a independent thermometer is at a constant 163F then one or the other is out of calibration. K type thermocouples can be as much as 2F off which is why the temperature of anything being controlled by a thermocouple needs to be independently verified. But one good thing about a K type thermocouple is once you know the offset you can count on it. In other words, of yours is +1/2 degree off it will always be +1/2 degree off.