What steering wheel are you using?
the GT one from argos, (logitec force GT) £81 this was made for GT5. if you get one you will never go back to the controller.
the best setting i found for the wheel is simulation and no power steering and leave the feedback at 5,
otherwise it is far to twitchy. i've not mastered the gears yet but all in good time.
but beware the throttle is more real and with back wheel drive cars you cant floor it round a corner or you just spin.