Hmm yea i'm not sure. I was thinking you had a piggyback system (such as emanage ultimate) that would allow you to wire in the extra map sensor for tuning purposes.
What makes you think its the map sensor causing you problems? What is the black box you speak of? I'm guessing its a form of voltage clamp?
Honestly, you should post your questions over on rs25.com as they have a much larger community regarding turbo'd NA subarus.