I don't think Congress should investigate this. Nor do I think the main Justice Department should. Because why? Because I don't trust either entity to handle the job: Congress was part of the problem, and whatever it does will be politicized, while the Obama Administration has made it very clear it does not want to turn over this rock.
Rather, I hope that the federal grand jury in Alexandria, Virginia, that I've been hearing rumors about for a few years, which supposedly is looking into CIA torture issues, expands its scope to look at CIA domestic abuses.