ecuExplorer is an open-source application that will connect to a Subaru ECU; 1999 model and onwards.

It can provide many diagnostic information parameters as well as being able to request user-defined parameters from the connected ECU.

It also has ECUFlash integration which will allow you to download the current ROM image off the ECU, compare a ROM image to what is currently loaded on the ECU and upload a new ROM image to the ECU. ECUFlash is another open-source initiative supplied from openecu.org