Same issue with my 1997 F355B.
A Ferrari tech I knew who was working on the cars when fairly new told me they fitted quite a few new units after complaints from owners but there was little or no difference in performance. Bottom line is the sender unit appears to be poorly designed or manufactured. 348/Mondial T anyway. Mine works but is slow to react. Especially at lower fuel levels. I fill up to 3/4 tank approx. only. I can live with it and after talking to the tech I don't think a new one would be significantly better. You might be able to fix a non working unit but maybe not the performance. Im all ears though.
So just fill up the tank when it is half empty and the problem is fixed? I guess this solution will also work when you're having problems with your gearbox?
Problem fixed: https://www.ferrarichat.com/forum/threads/new-ricambi-america-348-f355-fuel-sender-units.630167/ (aftermarket senders)
