Philnishma

Hi all I have a 33gtr possibly series 1 or 2 you drive along at light throttle and sometimes it will run rough and then come good again and some times it starts then turns off a couple times I have cleaned air flow meters and checked for fuel pressure when this happens fuel pressure sits at 2.5 bar when car starts and stops randomly and other times car is good not a hiccup at all what could this be?