Bring a large pot of lightly salted water to a boil. Add macaroni, and cook for 8 to 10 minutes or until al dente. Drain, and rinse under cold water. Put macaroni in a serving bowl, and mix in the marinara sauce, celery, relish, olives, onion, mayonnaise and chili powder. Cover and chill for at least 2 hours before serving.