Cook the pasta according to the packet instructions. Then drain and rinse in cold water until cool. Set aside.
Cut the bacon into 1/2-inch pieces and throw into a large skillet. Saute until slightly crisp, and then remove to a paper-towel-lined-plate.
For the dressing, mix the mayonnaise, milk, vinegar, salt, and sugar if using in a small bowl.
Stir together the pasta, dressing, tomatoes, bacon, Cheddar and green onions in a large mixing bowl. Taste for seasonings, adding more salt and pepper if needed.
Stir in the basil at the end.