I've read this thread with great interest.
I've had the PF Bushes on the front of my 159 Ti Q4 2.4 for about 18 months now. The squeaking started last Summer, and it drove me nuts. Not knowing until today that the likely (definate?) cause was the PowerFlex Bushes, I just knew it was front suspension, possibly even the Bilstein/Eibach Pro-Kit fitted about the same time. Back then, over time, I had two different garages throw cans of lubricant in the general direction of all suspension components, to absolutely no avail. (It was one of those many times in Alfa ownership when your head tells you to take the car into a field with a shovel and a shotgun, and walk out alone in pensive mood after some time has passed. - I will call this 'Plan A' - The heart of course wins, the Alfa gets more money thrown at it to fix whatever problem it has as always. You're all owners, you know what I'm saying. This is a tangent, back to the main story: ). Anyways, I lived with the squeak for a while (I didn't know what else to do), and then a miracle happened. THE SQUEAK STOPPED. This coincided with the end of warm weather.
My powers of reasoning tell me that this means, on my car at least, that either the problem is temperature related, or that whatever was squeaking was now so badly worn that it was now too slack to be bothered to squeak and was about to fail. As nothing broke, I went with the earlier option, and this view is reinforced by the above thread comments from others. I thank you all.
The new Plan A is to target the PF Bushes with the above recommended Wurths HHS 5000 Lubricant, and see if squeak returns with warm weather. I don't really have a Plan B, we'll cross that bridge....
I will keep you posted as to whether I have returned to my original Plan A.