I have to assume you are still using your air box since you have the K&N box filter, so how is sand getting to your filter? I realize that some dirt and sand will find its way into the air box, but the K&N can filter this stuff quite effectively. Did you modifiy your air box by drilling holes in it? If so, they make 12"x12" pieces of the outerwears material. Its water proof and will keep out sand. You can cut pieces that are bigger than the drilled holes and cover the holes. Or, you can order the TPI values, http://www.thunderproducts.com/tpi_valve.htm, to put in the holes.