I'm really looking at how you place the two probes inside the cooker and how you run your wires.
The way I did mine vs the thermometer on the wsm was off by 65 plus degrees for both food and smoker.
Thanks always for your help an advice.
I don't have a WSM but I have a Mini WSM. I just drilled some holes through the side of the chamber. I drilled one hole right at the grate level of the two grates and one hole right above the top grate for the meat probe. I put 3/16" rubber grommets in the two grate level holes to hold the probe.
Here you can see the three holes, two with grommets and the probe in the top grommet:
And here you can see the probe inside the chamber (to the right in the pic) with the grommet holding it in place just above the grate:
I don't have any pics but I replaced one of the bolts holding the grate supports with a grommet I purchased from BBQ Guru. I put my pit probe through that hole but the meat probe goes into the meat but the wire is between the smoker and the lid - with the shielded Maverick 732 cable I have not had any problems. The rubber cables may give you some problems over time.
There is a thread on here somewhere that shows you a mod made from lamp grommets.
Here it is...