Add oil to the pan and heat over medium-high heat. Add leeks and cook, stirring often, until just starting to brown, 3 to 6 minutes. Add the remaining garlic and cook until fragrant, 30 to 60 seconds. Stir in wine and crushed red pepper; cook until the wine is almost evaporated, 30 to 60 seconds. Stir in tomatoes and the reserved 1/2 cup pasta-cooking water. Bring to a simmer. Add the pasta and toss to coat with the sauce. Cook, tossing the pasta with tongs, until the sauce thickens, about 1 minute. Add 1/2 cup of the pancetta mixture and toss to combine. Serve topped with the remaining pancetta mixture.