The connectors of the wiring harnesses are hard to take out. You have to pull the clip towerd the outside of the ecu and pull on the connector at the same time. Than, on the left side you will see a small metal clip/bracket that hold the ECU in the tray. Move that to the left and you can pull the ecu out.
In the future, please post the questions in the apropriate sections of the forum. Even though this will lead to a power upgrade, it is not a power upgrade.