I don't know about the rest of the folks, but mine only get's hard when it get to the the middle... erm, what I mean to say is that when the steering wheel is centered again. (if it's responsive to rpm, shouldn't it be hard for the duration of time that it's at high rpm?)
maybe the speed sensor should be the one giving the pump it's instruction, after all, in low range, you've got tommes of rpm, but no speed??