Cook the macaroni according to the package directions. Drain and rinse under cold water to stop the cooking. Let cool completely.
In a small bowl, whisk together the mayonnaise, sour cream, mustard, vinegar, sugar, celery seed, salt, and pepper.
In a large bowl, add the cooled macaroni, eggs, celery, red onion, and pickles.
Pour the dressing over the salad and stir gently to combine. Cover and refrigerate for at least 1 hour before serving to let the flavors come together. Garnish with fresh parsley, if desired.