i rember reading a while back a interview with fred gibson(or someone of similar status in the nissan ring) about their group A cars.(in zoom magazine_
nissan were quiet guilty of pushing the rules. in the old bluebirds if while driving they turned the key even further it would let them run more boost. Nissan were also the only people who could measure the boost restrictors... the guy in the interview pretty much suggests that they could set it to watever they pleased. there were also various other "hints of cheating" , and something about a certain button on the dash that when questioned he wouldnt even answer.