Burgers:

In a small bowl stir together the steak sauce, ketchup, soy sauce, garlic paste, chili powder, cumin, Tabasco, and salt and pepper to taste until sauce is smooth.

In a large bowl stir together turkey, onion, breadcrumbs, and 1/4 cup sauce until combined well.

Form into six 3/4 inch-thick patties. Burgers may be prepared up to this point 1 day ahead and chilled, covered. 

Divide remaining sauce in half and put in separate bowls, half for brushing burgers on the grill and half for drizzling on cooked burgers. Chill sauce, covered.

Cole slaw:

In a large bowl, whisk together mayonnaise, vinegar, sugar, and mustard. Add remaining cole slaw ingredients and salt and pepper to taste and toss to combine well.

Cole slaw may be made 4 hours ahead and chilled, covered.

Barbecuing:

Prepare the grill. Grill burgers on an oiled rack set 5 to 6 inches over glowing coals, brushing frequently with barbecue sauce, 6 minutes on each side, or until cooked through.

Drizzle burgers with remaining barbecue sauce and serve with cole slaw in pita pockets.