The Supreme Court has ruled that Executive Priviledge exists but not to cover possible criminal activity. That's why it ruled against both Nixon and Clinton's claim of Executive Priviledge during criminal investigations. Try reading something beyond your political biases and you'll see your argument is baseless.

The Constitution provides for separation of powers between the different branches of government. Maintaining the Constitutional separation of powers is more important than avoiding "the appearance of impropriety", especially on a politically motivated witch hunt. Congress does have appropriate oversight authority over the Executive Branch but the GAO does not. Let those Congressional committees with authority on energy matters make the requests and that would be proper. Of course, those members of Congress that met with Enron lobbyists or took their campaign contributions should recuse themselves from the investigation. Yeah, in a pig's eye.

If the Legislative Branch can demand this sort of information from the Executive Branch, then turnabout is fair play. Why not have the Executive Branch demand the meeting minutes of congressional hearings and meetings, including all contacts between members of Congress and lobbyists? Of course, if the Executive were to make such demands, Congress would rightfully tell them to pound sand. The reverse is also true.