Stud the roast with the cloves and rub with the Smokey BBQ Rub. Place the roast in a slow cooker and top with the onions. Cover the roast with 2 cups of water and slow cook for 8 to 10 hours. Remove the pork, discard the cloves and layer of fat, as well as any water and grease remaining in the pot. When the pork is cool enough to handle, use a fork or your hands to shred and pull the meat apart. Return the meat to the slow cooker along with the barbecue sauce. Heat for 1 to 2 hours. Serve on your favorite roll.
Combine the granulated and brown sugars, chili powder, paprika, garlic powder, onion powder, pepper, salt, mustard and cayenne in a bowl and mix well. Store in an airtight container.