Place the cooked macaroni in a large bowl and set aside.
In a small bowl combine the sour cream, mayonnaise, sugar, vinegar, brown mustard, salt, and pepper. Mix well.
Add the cheddar cheese, bacon, celery, broccoli, pepper, and onion to the bowl with the macaroni. Toss to combine.
Add the dressing to the bowl with the pasta and vegetables. Mix well until everything is coated with the dressing.
Refrigerate until ready to serve.