I'm very elated with this guy, Amuro Tooru. He's the most interesting and mysterious person in DC right now.
First things first, my take: TOORU is BOURBON/SCAR AKAI
I think Amuro being a student of a police academy, as Date Wataru stated, is a key clue to Tooru's past. The following assumptions are still weak as I'm still on the process of re-watching/reading the important events that can help in deciphering Tooru's identity.
Tooru is a good and competitive detective.
Always finishing first and outdoing a great police detective in Date, as stated in the Takagi case, is a hard feat. Meaning, Tooru is really above-par when it comes to him being a detective, which leads to the popular theory of him acting dumb in his first case in DC.
Tooru joining the BO has something to do with Akai joining FBI.
My weak theory, for now, is that after attending the police academy with Date, something happened between him and Akai that sparked their rivalry. I'm not thinking of the accuracy of the dates and events that involved Akemi, which is one of the suspected reasons for their rivalry. After learning that Akai is an FBI agent, I assumed that Tooru might have joined BO to beat Akai.
I also agree with the theory that Tooru is out to find and kill Akai. He could have deduced already that there was something wrong with how Akai was killed by Kir. And therefore, is out to find where Akai is.
Lastly, I think Tooru is now on 'observation' mode. I also believe he already knows the capabilities of Conan, and supposedly, knows his real identity, being Shinichi Kudo. And with that explosive 800th chapter where the three (Sera, Tooru, Okiya) met, Tooru is out to know who Sera and Okiya really is. And I think the same applies for Sera and Okiya.