Boil chicken in 2 cups chicken broth plus 3 cups water for 15-20 minutes or until cooked through. Prepare pasta according to package directions.
Season chicken with garlic powder, salt and pepper.
Combine pasta, seasoned chicken, celery, onion, bell pepper, carrots, and grapes in large bowl. Mix well.
In a small bowl, combine mayonnaise, yogurt or sour cream, and lemon juice. Mix well.
Fold mayonnaise sauce into pasta mixture, stirring well to coat all the ingredients with sauce.
For best results, refrigerate at least one hour and up to 24 hours before serving.