Thor Windsport 29M Hi pitched whistling at freeway speed
Through other posts determined that the whistling noise comes from the front grill, typically at speeds above 55. Thor will provide a honeycomb wire mesh that is easily installed behind the existing grill (no instructions provided, I called Thor CS). This fix significantly reduced the whistling noise but there is still wind noise in the cabin. Taking a long trip next month will see if it is considered a good fix.