Rep. Mike Pence and Sen. Bob Corker recently spoke out in opposition to the Federal Reserve, seeing it's powers as too pervasive, opting to introduce legislation to cancel it's dual mandate of maintaining full employment and stable prices and instead have the Fed just focus on controlling inflation.
As far as the stated reasons for this spark of expediency, Pence was more combative when the Fed "unilaterally' announced its new spending, which he said was 'at odds with the goals of the American people..."
Corker on the other hand "opted a much more restrained tone, saying he merely wanted to provide clarity to the Fed’s mission and maintained that, while concerned about QE2, the legislation was not in response to it," saying further of QE2, "None of us really will know, until we look in the rearview mirror [after] these policies have played themselves out as to whether these were good or bad policies.”
Essentially it is ambiguous why Sen. Corker drafted this bill and also why he is concerned about the Fed at all.
Until the Fed is held accountable for it's actions, by an audit or otherwise, their "mandate" is to do whatever it pleases.