I don't have the 6600...what kind of sewing are you doing when you get the nests? Seams or FMQing or what? If it's seams, try using a "leaders and enders" - scraps of fabric that you put under the foot before you begin sewing, feeding your project right up under the foot immediately against/after the scrap, and sewing off again on a scrap at the end (like chain piecing). If you are FMQing - do you pull the bobbin thread up as you begin? Both of those things may help.