Cook pasta according to package directions. Rinse with cold water and set aside.Cut broccoli into bite size pieces.Wash grapes and leave whole, or if desired, cut in half.Whisk together mayonnaise and next 4 ingredients in a large bowl. Separate about half of the dressing and set aside in small bowl or cup, cover and set in refrigerator. Add broccoli, cooked pasta, and grapes to bowl with remaining dressing. Stir to coat pasta, broccoli and grapes. Cover and chill 3 hours or overnight.When ready to serve, add remaining dressing and bacon (if using) and toss. Sprinkle with sunflower seeds just before serving.