I'm going to get in trouble for this, but I have to say what I know to be true.
My mother is an Italian Jew, and she lived during the Second World War. She often told me as a child that Pope Pius XII did a lot to rescue Italian Jews, but that he did not PUBLICLY denounce the Nazi genocide of the Jews because he knew they would step up their killing of Jews (and go after Catholics more as well) if he did so. Because of this, he preferred to work behind the scenes. It is similar to the reason why Obama is not speaking out against the vote situation in Iran...because the last time American officials spoke out regarding events like this in Iran, the government took it out even more on the protesters.
She also had told me that Jewish leaders of that time spoke up in support of the Pope after the war, including Golda Meir and Albert Einstein. They would not have done this if he had, in fact, helped the Nazis or done nothing. On a personal level, in the 1970s I spent a lot of time in NYC staying with a friend, and during my time there I met a then-elderly Austrian Jewish woman who was helped to escape over the Alps from the Nazis. She was hidden in Catholic nunneries before making her way to the USA. I remember her having warm words for Pope Pius XII also.
There is a movie I saw in the 1970s, based on a true story, written by an Italian Jew named Alexander Ramati, called THE ASSISI UNDERGROUND. This movie details the rescue of Italian Jews in Assisi, Italy by Catholic monks and nuns.
I would also recommend these books for anyone wanting to know the true story of the wartime situation, including info on Pope Pius XII:
"Yours Is A Precious Witness"--Memoirs of Jews and Catholics in Wartime Italy by Margherita Marchione, c 1997, Paulist Press
"The Italians and the Holocaust" by Susan Zucotti (an Italian Jew), c 1987, Basic Books
"The Jews in Fascist Italy"--a history, by Renzo De Felice, c 2001, Enigma Books
I know this isn't what some of you would want to hear, but I can only tell what my own personal experience is with Italian Jews and other Jews who did personally live through that time in history. I'm old enough, thankfully, to have known them.