Stir together first 6 ingredients; remove half of mixture, and chill.
Place tenderloins in a shallow dish or heavy-duty zip-top plastic bag; pour remaining molasses mixture over tenderloins. Cover or seal, and chill at least 8 hours, turning occasionally.
Remove tenderlins from marinade, discarding marinade.
Grill tenderloins, covered with grill lid, over medium heat (300 to 350 degrees) about 25 minutes, turning occasionally.
Saute onion and garlic in 1 T. hot oil in a saucepan until tender. Add wine and broth; cook over medium-high heat, stirring occasionally, until mixture is reduced by three-fourths. Stir in remaining molasses mixture, and simmer 5 minutes. Pour throu a wire-mesh strainer, discarding onion and garlic; return to pan.
Stir together cornstarch and water. Stir into wine mixture.
Bring to boil over medium heat, stirring constantly. Boil, stirring constantly, 1 minute.
Stir in 1/2 teaspoons salt. Slice tenderloin and put on platter, pour sauce over.