Bring a medium pot of salted water to a boil. Add the macaroni and cook as the label directs. Drain and rinse under cold water; shake off the excess.
Whisk the mayonnaise, sour cream, barbecue sauce, relish, mustard and sugar in a large bowl. Add the macaroni, chicken, red bell pepper, celery, red onion and parsley. Season with salt and pepper and toss to coat. Chill before serving.