ShlomoZalman,
The Minhagim of Eretz Yisroel are not of Minhagei HaGra.
First of all, there are dozens of Kehillos in Eretz Yisroel and they are all different from each other.
Secondly, Rav Scheinberg holds that there is no such thing as Minhag Eretz Yisroel, because of the first of all, because Eretz Yisroel is a big “melting pot” where every Rav and Rebbe that comes here does whatever he wants.
Thirdly, what people think is Minhag HaGra is more often a set of customs that the Talmidei HaGra established when they arrived in Yerusalayim. It was not totally Minhagei HaGra, but rather a hodgepodge of customs cooked up as a compromise between them and the Sefaradim. From the beginning of their settlement here, for at least 60 years, Ashkenazim could not have their own Kehilla or shul, due to the aftermath of the ill-conceived Messianic craze led by Rabbi Yehudah Chassid and Chaim Malach.
Fourth, people only follow Minhag HaGra (and Minhag Arizal too, for that matter) here when it is convenient. For example, I see a lot of Litvishe saying Tashlich for a long time. They don’t follow Minhag HaGra in that. Most people make two Brachos on their Tefillin, not like the Gra. Just go through Maasei Rav and you will see just how many Minhagei HaGra are not practised.
And lastly, there are more Sefaradim and Chassidim here than anyone else, so who established that Minhag HaGra is the rule?