Trim fat from pork; cut into 4-6 smaller sections. Salt and pepper to taste; place in a 5-quart or larger slow cooker.
In food processor or blender, combine salsa, chicken broth, prunes, onions, peppers, garlic, oregano and cocoa; salt and pepper to taste.
Pour sauce over pork. Cook on HIGH 4-6 hours or LOW 8-10 hours or until fork tender.
Remove pork from slow cooker; shred. Place back in slow cooker with sauce; keep warm. Serve in tortillas with sour cream, cilantro, pico de gallo and limes.