help needed
 

need help , working on 99 ml320, with several dts codes , this ml have 93000 ml, last 39000 ml never been served exept oil change, i change MAS sensor, all spark plugs, O2 sensors for left (4,5,6) bank, all codes is gone exept 304 , 305 , 306, after all this i lift fuel rail and check all fuel injectors spray, they all working properly, same codes is there, was waiting for feul pressure tester from Snap-on , checked pressure today was 0 bars-5 PSI, i ordered fuel filter .
my ???? is why only 3 misfire codes , not all 6.
thanx