DownSouth recently posted up a home grown wind deflector for his JK rack. Just a section out of a PVC water pipe painted black and held on with a couple of clamps.
My JK also has a lot noise from the rack when fitted which I'd imagine would be similar to what you are getting Hunty, I've cut a section of pipe ready to go just have to get time to fit it. Here's a link to DownSouth's post:
http://www.ausjeepoffroad.com/forum/...postcount=1561