In large salad bowl, combine rotini, carrots, Broccoli, Mushrooms, bell peppers, and basil leaves. In medium bowl, combine Italian dressing and balsamic vinegar. Toss salad ingredients with 1.4 cup dressing mixture. Cover and refrigerate 4–6 hours to allow flavors to blend. Just before serving, toss avocados and remaining dressing with Pasta salad. Serve. Preparation time: 30 minutes. Refrigeration time: 4–6 hours.