I can't speak for the 03/04 guys, but the IRS Cobras do have a different feel and response in handling. The Cobra has what feels like a sharper turn-in with more feel for what the suspension is doing. I'm not sure about the ratio though.
Well I know for sure that I could make a much shorter turn (at slow speeds in a parking lot) in my 98 GT than the cobra. So I believe its a different ratio.