Complex sentence: Ferrari team members, especially Harvey Postlethwaite (the designer of the 126C2), are reported to have observed changes in Pironi's behaviour throughout the summer of 1982, including an absolute certainty that he would win the title.
Split into simpler sentences: Ferrari team members, especially Harvey Postlethwaite (the designer of the 126C2), are reported to have observed changes in Pironi's behaviour throughout the summer of 1982. Pironi was feeling an absolute certainty that he would win the title.