Bring a large pot of heavily salted water to a boil and cook the pasta according to the package directions. Drain, rinse with cold water, and set aside.

Place the bacon in a cold skillet, turn the heat to medium, and cook until crispy. Drain on paper towels.

In a large bowl, combine the mayonnaise, vinegar, garlic and onion powders, and pepper, mix well. Add the pasta shells, bacon, peas, and red onion. Mix well. Stir in the cheese and parsley. Taste and add salt and pepper if needed. For best results, refrigerate, covered, for at least 30 minutes before serving.