Bring a large pot of salted water to a boil. Cook the macaroni according to the package directions. Drain and rinse in a colander under cold water.
Place the mayonnaise, sour cream, milk and salt and pepper in a bowl and stir to combine. Add the drained cooled macaroni, and toss to combine. Add the tomatoes, bell pepper, onion, dill, parsley and relish and toss to combine very well.
Cover the salad and refrigerate for 4 to 24 hours. Bring to room temperature before serving and adjust the seasonings.