I am an Ashkenazi Jew who lives in Canada. I now go to a Chabad synagogue there and I find it insulting when I hear the Chabad Rabbis pray using there Ashkenazi accent (The Saf instead of Taf and mispronouncing some of the Hebrew words)!! Is that proper Hebrew?
HaRav Moshe Feinstein writes that all pronunciations of Hebrew which have been adopted by Jewish communities are proper Hebrew, much as English- whether spoken in England, in Boston, in Georgia or in Australia or South Africa- is still English. Belong to that Orthodox synagogue where the custom is most similar to what your father and grandfather davened and if this is impossible or irrelevant, to the Orthodox synagogue where you feel you can daven best.