1. Combine chili sauce, ketchup, vinegar, sugar and mustard in a small saucepan. Bring to a boil over medium-low heat. Reduce heat to low and simmer for one minute. Cover and set aside.Seasoning Mix:
2. Combine sugar, garlic salt and cayenne in small cup.
3. Heat gas or charcoal grill to medium-hot.Burgers:
4. Combine pork, mustard and 1-1/2 teaspoons of the Seasoning Mix. Shape into 6 patties about 3/4 inch thick. Place on a cookie sheet lined with plastic wrap. Sprinkle remaining Seasoning Mix over both sides of patties. With the back of a spoon press a 1/2-inch indentation in center of each burger for even grilling.
5. Using a long-handled brush, season rack with vegetable oil.
6. Grill patties 4 minutes. Turn; grill 4 minutes longer or until they register 160 degrees F on an instant-read thermometer.
7. Spoon 2 tablespoons coleslaw on bottom piece of each muffin. Top each with a burger, a generous tablespoon of BBQ Sauce, and muffin top. Serve extra sauce on the side.