Trim fat from pork. If necessary, cut pork to fit in a 3-1/2- or 4-quart slow cooker. Place pork in cooker. Add broth. Cover; cook on low-heat setting for 8 to 10 hours or on high-heat setting for 4 to 5 hours. Remove meat from cooker; discard broth. Using two forks, shred meat, discarding any fat. Reserve 2 cups of the meat. (Place remaining meat in an airtight container for another use; refrigerate up to 3 days or freeze up to 3 months.)
In a medium saucepan, combine reserved 2 cups meat and the enchilada sauce. Cover and cook over medium-low about 10 minutes or until heated through, stirring occasionally. Meanwhile, warm flour tortillas according to package directions.
To assemble tacos, place pork mixture in center of warm tortillas or in taco shells. Top as desired with lettuce, cheese, tomatoes, olives, and/or avocado. If desired, serve with sour cream. Makes 4 servings.