Remove cloth wrapping from meat; tie with string for rotisserie broiling.
Arrange meat evenly on spit, piercing through the center lengthwise.
Place broiler pan on bottom of compartment and broil meat on low heat broiling position 1 1/2 hours.
Change to high heat broiling position and continue broiling 1 hour longer or until desired doneness.
Meanwhile, combine mustard, flour, sugar and salt in 1-quart saucepan; blend in 2/3 cup water, stirring to dissolve all lumps.
Cook over medium heat, stirring constantly, until mixture thickens and boils.
Remove from heat; stir in vinegar and sour cream.
Slice pork with electric knife and serve with hot sauce.