Yes, they sent me the “Wind Noise Reducer” as
@DaBull pointed out after the initial sale. I believe it’s now included with the purchase of the rack.
After attaching it, I was still getting whistling above 70mph. I have a Thule cargo pod direct mounted to the rack and I wasn’t sure if that was the cause of the whistling or if the rack was the continued cause. On long trips, the noise was driving everyone nuts - especially the dogs. I, separately, purchased Leitner’s Wirelok Wire Guide System. The Wirelok Wire Guide System is the “Wind Noise Reducer”. I cut to size a piece to fit the underside T-slot channel of the front facing load bar. One on top (as shown in the assembly instructions) and one on the bottom eliminated the whistling. Now I just have wind noise that I don’t think is any worse than what I had before installing the rack.
My advice would be to add the bottom piece before mounting it to the roof. It was a challenge attaching it with the rack on the roof. The rack is perfect for my needs and I enjoy it so much more without the whistling.