In today's "Daily Halacha" from Rav Ovadya Yosef, the topic discussed is a convert, someone who converts in Eretz Yisrael specifically, with a background from ashkenazic countries, if he/she should take upon themselves the customs and liturgy from the ashkenazic communities from which they hail, or if they should/could choose the nusach and customs of the sephardim and bnei eidot hamizrach.

Rav Ovadya's psak is because we consider a convert to be like a newborn baby, he is not connected to the minhagim of the countries and region from which he hails.

Since, in our question, as a convert he is not connected to the minhagim of ashkenaz, so because he is converting in Eretz Yisrael he must accept upon himself the psak and minhagim of the rav of Eretz Yisrael, the Mechaber, the author of the Shulchan Aruch.

There is not even room for him to choose to be machmir according to the opinions of the Reman, in those situations where the Rema argues on the Mechaber, as he is not connected at all to minhagei ashkenaz, and just like technically, as a convert, he can even marry his sister and there is no factor in simply being machmir (we don't allow it for appearances sake, so people shouldn't think that in Judaism incest is ok, after knowing it is not ok as a non-Jew) - this convert in Eretz Yisrael must follow the Mechaber alone.

This is in line with Rav Ovadya's general opinion, stated frequently, that in Eretz Yisrael the minhag of the Sephardim was always the prevalent minhag ones, and the ashkenazim who came later must be submissive to the minhagim according to the Mechaber.

(Yet they still insist on going to study in the Ashkenazy schools... :-) )