Hi all. Need some tec help if anyone can help out. Got a problem with a bmn 170 with a misfire and poor starting. Just done some head work due to misfire and starting issue. 4 valves were leaking. Built up and got it running but dropped back on to 3 cylinders on road test. Possible blow back from no 4 cylinder around injector. What I need to know is should there be copper washer on injector as TPS says no and there wasn’t any fitted when injectors were removed. All other seals have been fitted. I believe this is a ppd engine.