Preheat your Yoder Smokers YS640 pellet grill to 250ºF, set up for smoking. Trim the skin and fat cap from the Boston Butt end of the shoulder. Trim any excess tissue and fat from the surface of the shoulder. Score the skin on the Picnic end of the shoulder, to allow the rub to penetrate the skin.
Using a marinade injector, inject the shoulder with Smoke on Wheels Pork Marinade & Injection in a grid pattern. Use a paper towel to remove the excess moisture from the surface of the meat. Season all surfaces (meat and skin) with the Cattleman’s Grill 8 Second Ride Carne Asada Seasoning and Plowboys BBQ Yardbird Rub. Smoke on the second shelf, until the surface of the meat is a dark red mahogany color, about 4 hours.
Remove the shoulder from the cooker. Wrap tightly with foil. Include about X cup Smoke on Wheels Pork Marinade & Injection in the wrap. Return to the smoker and continue cooking until the meat is tender enough to pull, and the shank and blade bone can easily be pulled out of the roast, about 6 hours longer. The internal temperature will be around 195ºF. Rest the shoulder for 30 minutes before pulling the meat.
To make the grits, place the grits in a 10” Lodge Logic cast iron skillet, and cover them with 2½ cups water. Stir once. Allow the grits to settle a full minute, tilt the pan, and skim off and discard the chaff and hulls with a fine tea strainer. Cover and let the grits soak overnight at room temperature. If you are not soaking the grits, proceed directly to the next step.
Set the saucepan over medium heat and bring the mixture to a simmer, stirring constantly with a wooden spoon, until the first starch takes hold, 5 to 8 minutes. Reduce the heat to the lowest possible setting and cover the pan. Meanwhile, heat 2 cups of water in a small saucepan and keep hot. Every 10 minutes or so, uncover the grits and stir them; each time you find them thick enough to hold the spoon upright, stir in a small amount of the hot water, adding about 1½ cups water or more in 4 or 5 additions. Cook until the grits are creamy and tender throughout, but not mushy, and hold their shape on a spoon, about 50 minutes if the grits were soaked or about 90 minutes if they weren’t. Add 1 teaspoon of salt halfway through the cooking time. To finish, stir in the butter and cheese with vigorous strokes. Add more salt, if desired, and the pepper, to taste.