Cook pasta as directed on package. Drain well.
Meanwhile, mix milk, pumpkin, Parmesan cheese, flour, pumpkin pie spice, chipotle chili pepper and salt in medium bowl until well blended. Set aside. Cook bacon in large skillet on medium-high heat until slightly crisp. Remove bacon. Drain on paper towels. Set aside.
Remove all but 2 tablespoons bacon drippings from skillet. Add onion; cook and stir 3 minutes or softened. Stir in pumpkin mixture. Reduce heat to low; simmer 10 minutes or until thickened, stirring occasionally.
Place pasta in serving bowl. Add pumpkin sauce; toss to coat well. Top with crisp bacon.