Cook 3 cups macaroni according to the package instructions in abundant salted water until al dente. Drain, toss lightly with 1 tablespoon oil and let cool completely. You can also rinse the elbows under cold water to stop the cooking. I find that it strips them of some of its flavor, so I let them cool down on their own.
In a large bowl, stir together the cold pasta, ½ cup chopped bell peppers, ½ cup onion and ½ cup chopped celery.
To make the creamy dressing, mix all the dressing ingredients (2 tablespoons sour cream, ½ cup mayonnaise, 1 to 2 tablespoons apple cider vinegar, 1 teaspoon Dijon or brown mustard, ⅓ teaspoon salt, ⅛ teaspoon black pepper, and 1 tablespoon sugar) in a small or medium bowl until smooth.
Add half of it to the bowl with the pasta.
Mix everything thoroughly and add more until you have the desired consistency. Taste the pasta salad and adjust the seasonings to your liking.
Place the salad in the serving bowl or platter, cover it with plastic wrap and refrigerate for half an hour to an hour.
Stir the salad again before serving it cold.