PLYMOUTH, MICH. -- A key to Chrysler Group's return to profitability is a plant performance improvement program developed by parent company Fiat SpA (IW 1000/87) , said Mauro Pino, the company's head of World Class Manufacturing at the Machines Italia manufacturing 3.0 conference in Plymouth, Mich., Thursday, June 21, 2012 Chrysler first implemented Fiat's program, called World Class…