Slow-Cooker Pulled Pork Sandwiches

In small bowl, mix 3 tablespoons brown sugar, the chili powder, 2 teaspoons salt and the pepper. Rub mixture all over pork. Place in 4 1/2- to 5-quart slow cooker. Pour stock and 1/4 cup of the vinegar over pork. Cover and cook on High heat setting 4 hours. In medium bowl, beat mayonnaise, 3 tablespoons vinegar, 2 tablespoons brown sugar and 1/4 teaspoon salt. Stir in coleslaw mix. Cover and refrigerate at least 30 minutes but no longer than 4 hours. Remove pork to cutting board, and shred using 2 forks. Reserve 1 cup of the cooking liquid. Discard remaining cooking liquid. In medium bowl, mix reserved cooking liquid with barbecue sauce and remaining 1/4 cup vinegar; return to slow cooker with shredded pork. Cover and cook on Low heat setting about 20 minutes or until warmed. Using slotted spoon, spoon about 1/2 cup pork mixture on bottom half of each bun. Top each with about 1/4 cup coleslaw. Cover with top halves of buns. Pork mixture can be kept warm on Low heat setting up to 2 hours; stir occasionally.