Problem with stang

did you install it yourself?

what is your idle set at?

Did it come with a different pulley or is this with your pulley on it?

It does sound like the pump is not spinning fast enough to build adequate pressure. This could be from wrong idle set-point, wrong pulley diameter for the pump, underdrive pulleys, or even jsut junk in the system making the pressure it does build inadequate.

If it was OK when first installed and since the old one failed I would do what I could to flush the system... $10 worth of ATF can save a whole lotta trouble...

I flush mine every 6-10k miles since mine (like msot of yours) have HORRID looking and smelling fluid in it. Each time it gets just a little bit better...