I had the same problem, in fact I noticed all the 355's I test drove had sqealing brakes. The fix is to use Porterfield R4S pads. These are a high performance street oriented pad. They have noticeably better initial "bite" or friction compared to the stock Ferrari pads (Ferodo?). You can get them from many sources. Daniel at Ricambi stocks them. Same size for front and rear.
348 and 355 brake pads are directional. Try flipping the squeaky pads before buying new ones. Could be a free fix. If your brakes still squeak, then have your rotors turned down and install some good new pads (I'm a big, big, BIG fan of Axxis Metal Masters, but go with any non-race pad to avoid squeaks).
Another one on the winter to-do list; partially for the annoying squeak, and partially for the terrible stopping force.
