I ran full time E85 when my car was running.
Now that I am reviving my wrx I am going to try and use an innovative e85 flex fuel wide band kit paired with the carberry rom so I can get an actual flex fuel setup going incase I need to fill up with 91 sometime. I don't know how it will work since I haven't tried it yet, so I don't want to tell you to go this route but maybe look into it.
Here is a link to the innovative setup.
https://www.innovatemotorsports.com/products/ecf1.php
Edit* is this an sti with a bugeye front end? It looks like it has DBW throttle body so gonna say it is. In that case carberry rom won't work on that 32 bit ecu but I am sure your able to set up the innovative setup another way.