I have the same problem after about 2 years. I have another shopping cart on a different directory that have 1000 000 items but the cs cart struggles. I know some people are going to say t is me not cs cart, but if you compare it to other carts you need to do a lot of seo work for not much results. Even my sitemaps submitted to google has been crawled less than 7%. I did not even need to list sitemaps on the other sites.