i was reading an article here http://www.snowtechmagazine.com/articles/dontuse/dontuse.html about diff. jet sizes. *they say not to use the 520 main jet sizes because it is actually smaller then the 500 main. *they give a conversion chart *like the 540 main, is now called the 510N, what is with this??

That's exactly right...DON'T USE THE 520'S!!!!!!!!!!