Mazda Familia Cutting out problem
 

Got a Mazda Familia import 1.5 (1997) It will only start cutting out once the engine has properly warmed up (after about 15min of driving)while keeping the RPM's at 3500 constantly. I've tried everything I can think of to fix this problem - I know its loosing spark, I have put a fuel gauge on it and drove with it until it cut out and the pressure was still up there and have come to realise the car is loosing spark while a timing light was fitted and keeping the RPM's at 3500. Would be interesting to hear some of your views on this! Have replaced both ignition coils and fuel pump.