If you want to join your boyfriend here on basis of partnership, they call it "ricongiungimento familiare", then the application must start in Italy, where your boyfriend will go to the police headquarters (Questura) and request a Clearance (Nulla Osta) and his intent to marry you.
After that, the police will transmit an electronic copy to Taiwan for your visa. I dont know if you must be married at the moment of application, but it's best you check with them because requirements vary.
Hope this helps, but again I must stress that it must be a "contra-entry" procedure as it MUST start in Italy and your boyfriend must initiate it.
Hope this helps, you can ask me for clarifications or any other information.