Assuming the brakes have been bled, have fairly recent brake fluid,
and all the cylinder pistons move freely, a safety requirement anyway,
then squeal tends to be a function of friction material composition.
If you have bought branded pads then most mfrs have a website
with a contact us. That's who to ask. My experience is that
pads, and bonding to the backplate materials, use some organic
components, which can initiate a rapid (squeal) grab and release
action, some seem to have a small amount of embedded copper
(not sure if it's copper) to prevent this.
There are cheap pads and quality pads, you get what you pay for,
in the UK I prefer Mintex. Some brads don't seem to have the
stopping power of others (Tapley brake meter and Smiths
Instruments accelerometer). I'm not too sure if the MOT rolling
resistance test, with cold disks, truly emulates emergency
braking.
I'm also very surprised, in view of safety issues, why tyres
(tires to the Yanks) have to meet specifications, as do bulbs,
but not brake components.
There is a very good Fiat forum at
http://www.fiatforum.com/
and searches there about Fiat problems yield a wealth
of info based on members experience with various problems.
I have often used it to help with how do I replace/remove or
get at problems.