Again i can't claim the credit but am happy to share this with you.
The recipe would make a huge batch but i normally make a quarter of this and that lasts me a few weeks.
2 Litres Ketchup
2 cups Apple Cider Vinegar
1/2 cup Sugar
1-2 tbs. Garlic Powder
1 tbs. Celery Seed
1 tbs. Ground Cumin
1 tbs. Chili Powder
1-2 tbs.Cayenne Powder
1/8th cup Coarse Salt
1/2-1 cup Water
Then cook the sauce for 10 minutes to reduce it to the consitency desired, and this will also help mix the additional spices to the ketchup.
Good on it's own, or add a bit more water and use it as a mopping sauce to go with the simple rub