Halve eggs lengthwise and remove the yolk, reserving the whites. Add the yolks to a mixing bowl along with the mayonnaise, vinegar, mustard, and salt. Mix for a few minutes on medium speed until smooth.
Spoon half the yolk mixture into a pastry or food bag (or add to whites with a spoon) and fill 12 of the egg whites.
Add the truffle oil to the remaining yolk mixture and mix well. Fill the remaining 12 egg whites with the truffle yolk mixture.
Garnish half of each with bacon and half with green onions. Keep refrigerated.