Pepsi Barbecue Sauce

2 tablespoons butter
1 onion, finely chopped
1 teaspoon garlic powder
1 teaspoon onion salt
2 cups ketchup
1 (12 ounce) can Pepsi
1 tablespoon Worcestershire sauce
1 tablespoon prepared mustard
2 teaspoons vinegar
1 cup brown sugar
2 tablespoons Open Pit BBQ sauce
Salt and pepper to taste

Bring all ingredients to a boil, then simmer for 1 hour.