Combine rub ingredients and thoroughly rub into pork. Cover and refrigerate 8 to 24 hours.

Combine all sauce ingredients and set aside.

In a large skillet or pot, heat 2 tbsp of the vegetable oil over medium high heat; brown pork on all sides. Transfer to slow cooker.

In same skillet or pot, heat remaining 1 tbsp vegetable oil and cook onions over medium heat until softened. Add garlic and cook an additional minute. Stir in sauce and bring to a boil; cook and stir for 2 to 3 minutes.

Pour heated sauce over pork in slow cooker. Cover and cook 6 to 7 hours on low heat.

Remove from cooker; cover with foil and let stand 15 minutes. Shred pork using two forks.

While pork is standing; skim fat from liquid in slow cooker. Pour liquid ionto a large pot and bring to a boil. Add shredded pork and cook until heated through.

Warm tortillas or taco shells according to package directions.

Fill warmed shells with pulled pork mixture and top as desired.