Stir together the chile powder, salt, sugar, cumin, oregano, garlic powder, red pepper flakes and garlic in a large mixing bowl. Add the whole pork shoulder and rub with the spice mix to coat evenly.
Bring a large skillet to medium-high heat and add the vegetable oil. Use tongs to transfer the shoulder to the skillet, and brown for 2 to 3 minutes on each side.
Remove from the skillet and place into a slow cooker on high heat. Let cook for 3 and a half hours, at which point you should be able to easily shred the pork with two forks. Shred the pork and let cook on low for another hour.
When the pork is nearly finished, start preparing the sweet potatoes.
Preheat the oven to 425 degrees F degrees. Cook the chorizo in a cast-iron skillet over medium-high heat for about 3 minutes until the fat begins to render. Add the sweet potatoes, then lower heat to medium and cook for another 5 minutes.
Transfer the skillet to the oven and roast for 20 minutes, stirring occasionally, making sure the potatoes don’t blacken. Remove the skillet from the oven and set aside.
Make the pico de gallo by combining the chopped red onion, tomato, cilantro, jalapeño, lime juice and salt and pepper.
When ready to serve, brush both sides of the tortillas with olive oil, and grill on a hot grill or stovetop griddle for about 2 minutes on each side. Assemble the tacos by piling on the pulled pork followed by the sweet potatoes and chorizo, pico de gallo, sour cream and a squeeze of lime.