Am I allowed to use a Temani Hebrew pronunciation but keep Ashkenazi customs and Nusach?

Shalom, Thank you for your question. There is much debate in the sources as to the correct pronunciation of Hebrew, and how much this is important to fulfill ones obligations in prayer and Torah reading. The general consensus is that one should continue to follow their family custom, however if they have been educated with a different accent (such as being sent to a school where they were taught with a different accent), then there are Rabbis who say they should try to revert to their parental custom, and others who say they may continue with their present accent. It is generally agreed upon that no matter how one pronounces the words (whether like their family custom or not) they do in fact fulfill their obligations of prayer and Torah reading. This is because no particular accent is any “better” or more correct than another. All accents (including the Temani one) have their faults – and we have lost the original Hebrew pronunciation. The major question is whether one should make the effort to change their accent or not. With no accent being better than another, why change way for another – unless it is to gain the benefits of continuing family traditions, or being part of your community. In your case I would like to understand why you want to make to make a change to use Temani (Yemanite) pronunciation? Are you part of a Temani community? Do you have a reason to make such a change? If there is no reason to make such a change (other than the fact that you personally like their pronunciation), and you are part of a Ashkanazi community, and follow Ashkanazi customs – then to change to Temani pronunciation is improper. One should try to become part of their community and family customs, and strive to be “normal” in relation to their Judaism, rather than looking for different special practices that separate them from the community and their traditions. There are so many places where a person can put their efforts to find their own personal way to serve Hashem within the framework of their own community and traditions that they should not look to foreign pastures. For example why not try to pray with more passion, saying Tehillim, learning every day after prayers etc etc. In conclusion – from a technical point of view someone who in Ashkanazi but uses a Temani accent would fulfill their obligations. However, in general, a person should continue their family and communal customs. Blessings.