2003 discovery misfire code po306

Question:
I have a 03 discovery misfire code po306 i changed plugs,wires, coils, performed leakdown test ok, comp is 180 ,fuel psi is 55 checked for vacuum leak ok ,do you think the problem is the fuel injector. have you ever seen this problem before on a land rover. also i looked in the cylinder and the center of the piston is clean, spark plug is black

Answer:
From what you are describing I would Say it is definitely the injector being stuck open. You have eliminated most of the other reason it could be doing this. About the only other thing that might cause this would be the O2 Sensors giving false reading. If all the plugs look black on that side of the engine and not just #6. Replacing just the front O2Sensor would correct this.