Place the roast in a dutch oven.
Add broth, onion, and celery.
Bring to a boil, reduce heat cover and simmer for 2 1/2 -3 hours until tender.
Remove roast, cool, and shred with 2 forks.
Strain veggies and reserve cooking liquid.
Stir in ketchup, brown sugar, vinegar, salt, mustard, Worcestershire sauce, garlic, bay leaf, garlic powder, paprika.
Reduce heat, cover, simmer for 30 minutes.
Discard bay leaf.