The only captured P-38 ever used by the Italians was one that was captured when the USAAF pilot landed in Italy by mistake during a ferry mission in '43.
Col. Angelo Tondi did claim a B-17 shot down but the P-38 was eventually grounded and rendered useless by the poor grade of gasoline that the Italians were using. The other P-38 that fell into the Italian's hands (courtesy of 2Lt. Martin Monti who defected to the Axis), was a recon P-38 (F-5E) and it was handed over to the Germans.
None of the YB-40 gunships were ever used in southern Europe and/or the MTO, all being deployed on missions over France or Germany (and one aborted raid targeting Bergen, Norway).