You will find 216 to be harder than both 210 and 215. If you have Transcender and understand the explanations they are providing, then you have a great simulator already. If you don't understand the explanation try to search for more information either in your books or here, online.
Take your time preparing for this test. This one deserves the title it has of "the beast" and requires a lot of concentration at test time. So don't rush yourself.