Boil chicken until no sign of pink. Let cool and refrigerate.
Cube meat and place in large mixing bowl.
Add celery, apples, grapes and pecans to chicken.
In a small bowl, combine mayonnaise or yogurt, sugar and vinegar. You'll need to check to your taste. Add sugar if too tart, vinegar if not tart enough. Can add a little milk if it's too thick. Mix well and add to chicken mix and mix well.
To serve, lay tortilla flat, place a leaf of lettuce toward middle more toward one side. Add a couple of good spoonfuls of mixture, fold one end up to bottom of lettuce, then fold wrap from one side, rolling until wrapped up.