Opencart google feed and sitemap running out of memory (200,000 items in store)

I am having trouble with the this google products/sitemap generator mod. [login to view URL] We have about 190,000 items for sale and this mod allows you to split your google feed into smaller feeds. I would like to run 50,000 itesm per feed since we have so many items in our store. But our server is running out of memory not matter how high the memory is set. Even when I run the script at only 5,000 items, I get the following error from the server. Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 19156315 bytes) in /home/gobstock/public_html/system/library/[login to view URL] on line 38 I contacted my host and they said. "We have raised the limit to 256 MB but the script still output an error. We then attempted to raise the limit to as high as 512 MB but were still hitting a limit. In this situation it would be highly suggested that you optimize the script or consider using a different product." The same mod also creates google sitemaps and we are having the same problem. That would also need to be fixed. We are running opencart version 1.5.2.1