Sprinkle 3/4 teaspoon salt and 1/4 teaspoon pepper over roast. In a large skillet, brown pork in oil on all sides. Transfer meat to a 3- or 4-qt. slow cooker.
In the same skillet, saute onion until tender. Add garlic; cook 1 minute longer. Add water, chipotle peppers and molasses, stirring to loosen browned bits from pan. Pour over pork. Cover and cook on high for 4-5 hours or until meat is tender.
Remove roast; cool slightly. Skim fat from cooking juices. Shred pork with two forks and return to slow cooker; heat through. In a large bowl, combine the coleslaw mix, mango, lime juice, lime peel and remaining salt and pepper.
Place muffin halves cut side down on an ungreased baking sheet. Broil 4 in. from the heat for 2-3 minutes or until lightly toasted. Serve pork with muffins; top with slaw.