Boil and cook the macaroni as directed on box, but then cook it two or three minutes longer. The noodles need to be really soft and fat.
Drain noodle and pour them back into pan. Stir in the vinegar, cover, and let stand at least 10 minutes so that the vinegar soaks into the noodles.
Combine mayo, milk and brown sugar. Stir into noodles.
Stir grated onions and carrots into mixture.
Season with salt and freshly ground pepper.
Refrigerate until cold. Can last about four days.