Rosh HaShanah and Yom Kippur

[Mattityahu ben Noach]

As a Noahide, here are some guidelines for the Jewish Biblical festivals:

[...]
6) You can follow along in the Orthodox Jewish prayer book during the services, but don't recite those parts that apply exclusively to Jews. Gentiles may bow down to the floor in prayer while the the congregation does so during the Rosh HaShanah and Yom Kippur services.

How will we know which portions that apply exclusively to Jews? It is my experience that since a Siddur is (almost always) designed for Jews, they (almost) never specify which portions are for Jews alone. [They may, however, denote which words are specifically for a Levite or a Cohen]. As a possible (temporary) fix to the 'problem', can one omit words or phrases (even at random) so that we are NOT reciting the (complete) prayer as would a Jew?