Bring a large pot of lightly salted water to a boil; cook the rotini at a boil until tender yet firm to the bite, about 8 minutes; drain. Rinse in cold water until rotini are cold and place in a large bowl.

While pasta cooks, mix mayonnaise, pickles, mustard, vinegar, sugar, pepper, celery salt, and garlic powder together in a bowl. Stir dressing into cold noodles until fully coated. Add additional pickle chunks to taste. Serve chilled.