I also have ancestors from San Pietro Avellana and the town does still exist, although it isn't a "boom town". The town has a website (in Italian) at www.comunesanpietroavellana.com
I understand that the town was occupied by Germans during WWII, then liberated by Americans in 1944. Most of the records of the town were lost during the wars but the LDS has microfilmed the ones that remain.
My g-grandparents were Antonio R. Carlini(o) and Lucia Mariani, who came to the state of Colorado in the early 1900's and raised their family there.