grinding noise with MSDS

It's probably your wallet returning to its rightful position on the right side of your ass.

The headers don't come anywhere near anything that's spinning. The closest thing is the right axle shaft, but that's in a bearing and harness- Doesn't start flexing until well past the headers.

Looks like someone may have messed with something else while under there. Who installed the headers?

Ford's power steering pumps "hummm" by nature, it is usually heard when steering at slow speeds. If you're sure the noise you're hearing is new, I'm not sure what could be wrong.

I didn't think they were available for ATX yet...

They've had ATX as long as MTX, no difference except the flang connection.
Mine is on the way (hopfully) and it's an ATX.

For the headers i agree with DANG. THey must have messed with something else down there, and if you have an ATX they definitely messed with something else anyway because of everything being in the way.

Hey if you do have an ATX let me know how much power you got out of em'.
Was it worth the money to buy them and have them installed?

You sure you don't have the problem I did a while back? Maybe you have a wheel bearing going bad?