There were a few power steering pumps replaced under warranty in the US based on the informal polling I did here on the Forum. That said, I'm not convinced it was really needed. Several GT that I have worked on (including my own '06 #1208) showed evidence of a leaking pump at the first oil change. However, in my car and others that I have serviced, there was NO evidence of leaking at subsequent service intervals. My speculation is that perhaps there was an over-fill situation from the factory - or o-rings or something that needed to swell.
Back to your issue, I would think that the rack, the pump, and suspension settings are the primary suspects - perhaps even in that order. Replacement of the rack itself did not solve the problem, so I would very much have the pump itself at the top of the suspect list. Maybe, for example, it is not providing sufficient pressure. This could be the cause even though all outward appearances would be "normal".