Place ribs in a large pot, and cover with water. Cover, and simmer for 1 hour, or until meat is tender.
Drain, and transfer ribs to a shallow dish.
In a small saucepan, stir together the maple syrup, brown sugar, ketchup, vinegar, Worcestershire sauce, salt, and mustard powder. Bring to a low boil, and cook for 5 minutes, stirring frequently. Cool slightly, then pour over ribs, and marinate in the refrigerator for 2 hours.
Prepare grill for cooking with indirect heat.
Remove ribs from marinade.
Transfer marinade to a small saucepan, and boil for several minutes.
Lightly oil grate. Cook for about 20 minutes, basting with the cooked marinade frequently, until nicely glazed.
