Seeking guidance-Kozi king furnace 80/20 component

Hello, i have a very good childhood friend needing help with his DS Kozi king furnace. I went over and fixed most of it and set it up correctly, but he is very concerned about the 80/20 electrical box on the bottom right, above cold air return intake. I typed it all out and went to submit but was timed out and lost it all, so ill keep it short, but he just thinks "its way too hot and was humming". He was running the furnace incorrectly and with the wrong fuel, so when i tweaked everything it must have resolved a little because he kept saying "of course it won't happen when you're here!!" I temp gunned it from multiple angles and on different surfaces and never exceeded 104F, i attempted to explain that he has one of the best built furnaces available today and 100F for any electrical components is fine, especially sitting on a monster furnace. Can someone please break down its function for me so i can translate into layman's terms? It wasn't covered much in the manual and searching here got me one unrelated post. I just want him to be safe, i converted him to the dark side in less than an hour with not even a full 5 gallon bucket lol but i told him to clean his stack today before switching completely. when its down today , i want to make sure its running ok and his family is safe after its set up properly and running again. I THINK its fine, but im not willing to gamble his 5 kids on my very limited experience with a coal furnace and a few hours of reading about them, especially electronics.

Hmm, what is one of those?

pictures...
some links to a diagram...

combustion bypass...
Here is a link to photos of the KK...
Tell us which picture the device you are worried about...
https://messickstove.com/products/ds-machine-stov ... index.html

Ahh, THAT makes complete sense!! Thanks Cape, plus it reminded me about the louvers, that i think i read help ensure fresh air is always coming in to to reduce visits from Puff the Magic Dragon. I was excited to see him, and maybe a little to see the furnace as well, so i forgot to tell him some things and he got worried during the puffback example i showed him. after we finished setting him up it was well past time for tending my Harman, so i just drug him along with me because it turns out he's only 5 minutes away next to the Simplicity dealer. He was amazed how warm my entire house was with such a small pile of coal still burning in an insert. More money feeding hard working Pennsylvanians, more family time for him, and less oil dependency. I appreciate your help.

EDITED......It unfortunately isn't on any of those pictures, picture 28 is the closest (**EDIT.. I was wrong, it is there on pic 28, but oriented differently than his, couldnt zoom in enough, its on the bottom of the thermostat wiring in pic 28 while his is to the right, his draft fan is also reversed from their pics). I figured it out while reading but then re read your post and realized you were telling me to use the pics to come back and describe it better. I know pics help but i didn't take any and its not on messicks, sorry i just thought someone who owned one would know what i meant. We should be good with the knowledge you provided through that link, thanks again. ... We are now even better, i am going to be able to really help him save money and time now with messicks info, I've been there 100 times (mostly to ogle the insert and see if i can squeeze a circulator on my hearth ) but always figure if specs are not on manufacturers site, it won't be on dealer, this is why i read things repeatedly lol, sorry