Heat oil in large skillet over medium-high heat. Add garlic and roast. Sear on all sides (2-3 minutes) until slightly browned on all sides.
Place roast in crock pot. Add peppers to the browned garlic left in the pan. Add chicken stock, simmer and stir until all browned bits are lifted. Pour liquid into crock pot. Cover and cook on low for 8 hours.
Remove roast from crock pot; place in shallow bowl and pull apart with two forks.
Meanwhile reduce liquid from crock pot by placing into a pan over high heat and bring to a boil. Reduce to about 2/3 cup. Add liquid to pulled pork.
Warm tortillas. Add pork to tortillas, top with spicy chimichurri sauce and a dollop of sour cream. Enjoy!