Cook noodles according to package. In the last minute of the remaining cooking time, add the snap peas. Drain noodles and peas.
In a large bowl, whisk together the peanut butter, vinegar, tamari, chili flakes, garlic and ginger. Add splashes of warm water a tablespoon at a time, to thin the sauce so that it'll coat the noodles and vegetables. Add the noodles, snap peas, carrots, bell pepper, green onions and sesame seeds. Toss to coat, garnish with peanuts and serve at room temperature or chilled.