Cook the pasta according to package directions. Drain, rinse under cold water, and drain again.
Meanwhile, cook the bacon in a skillet over medium-high heat, turning halfway through, until crisp. Transfer to a paper towel-lined plate to drain; crumble.
In a very large bowl, stir together the mayonnaise, ranch dressing mix, vinegar, garlic pepper and garlic powder. Stir in the milk until smooth. Add the cooked pasta, crumbled bacon, tomato, cheese and olives to the bowl; toss to coat. Chill, covered, at least 1 hour to allow the flavors to meld. If the salad seems dry after chilling, toss with a little more milk, as needed. Garnish with parsley