BERLIN/PARIS, July 15 (Reuters) – Carmakers are racing for Iran following the country’s breakthrough nuclear deal with western powers – pitting past market leader PSA Peugeot Citroen against challengers such as Volkswagen. Within hours of the announcement of a final deal on Tuesday, Paris-based Peugeot had outlined plans for new Iranian production to reclaim and defend the leading market position it held before sanctions were tightened four years ago.