agha33, I'm not entirely satisfied that you understand what I mean. I just want to be completely sure that all avenues have been explored before you shell out on a new rack.
When I said track rod ends, you may know these as steering rods or arms. If there is in and out play on these (grabbing either front wheel when front of car is off the deck, position hands at quarter to 3 on the roadwheel) this would be detected be rocking or trying to turn (slightly to and fro)the front wheel (as if steering).
Any immediate free play (movement in the first 2 to 3mm may indicate free play in the rods or lift in the rack. (The guides in the rack can wear and produce slight vertical lift in the rack itself). I have not ever seen this in an Alfa or Fiat of this type though.
If you notice a feeling of free play by vigorously rocking the rack with some force, this is most likely just the hydraulic rams in the power steering rack moving the fluid until the valve prevents any further movement. This is normal and the rack is probably ok.
When the car is on the ground as normal. hold the steering wheel at the quarter to three postion with fingertips. If there is any noticeable free play when rocking to and fro (by moving no more than half an inch with engine running), then there is probably wear in either the steering column or rack. You would then have to ensure that there is no relative movement in the steering column joints or even if the steering wheel is loose on its splines on the column!
Hope I haven't been too long winded, but just trying to help. If this dosen't make sense, post a reply and I'll try to help further.
I'm not sure where the clunking noises may come from though. Perhaps you could mention under what conditions they occur.
You do seem to know your way about though, and I think that you have adjusted the free play from other racks?