Pork butt is super forgiving, and has a wide range of "acceptable" internal temperatures, so once you find the internal temp that works best for your personal preference, it's as easy as just letting your thermometer tell you when it's done. Pork butt can be removed and wrapped anywhere from 190 to 205 degrees internal temperature. I smoke at 225 degrees smoker temp. I prefer smoking butts to a higher internal temperature than many people here, more like 200-205, with a long 2-3 hour rest in a cooler wrapped in foil and towels. I want it to completely fall-apart. Some people like more "texture", so that's where you might find the 190-195 folks. I've tried that, but it doesn't seem as moist and succulent to me. I think the "stick a finger in it" is most likely around the 200 mark. But with the SIs, sticking a finger in requires opening and closing the door, which releases precious moisture and heat, and can really extend your smoking time. You should be able to get excellent results on pork butt by going by the internal temperature that works best for your tastes.