In large pot of salted boiling water, cook pasta until al dente, rinse under cold water and drain. In medium bowl combine mayonnaise, sour cream, milk and Italian dressing mix. Whisk together until smooth, set aside. In large salad bowl combine cooked and cooled pasta, peas, olives, salami, green onions, celery and parsley. Mix in dressing last, reserving 1/2 cup. Let sit overnight in fridge.
Stir before serving. Add extra dressing if pasta appears dry.
Chill overnight in refrigerator and serve as a main course with crusty bread and a hearty red wine.