I relaced all 4 O2 sensors on my 2004 Disco II only to have more codes come up. They read as follows: P0150, P0174, MIL ON, MONITRS, 3 Inc, Catlyst, Evap, O2 Snsr, 5 Ready, Misfire, Fuel, Comp, Sec Air, O2 Htr. I used O2 sensors bought from Atlantic British.

 

You did it backwards, you need a tune up, that means new spark plugs and spark plug wires.
98% of all Land Rover O2 codes are due to the severe need of a tune up, thats why you have the mis fire codes.
Do the tune up, clear the codes and see what, if any, come back.

 

And recheck your codes, this time send us all your 4 digit fault code numbers so we can help you.

 

I've been chasing this issue for a couple of months now. I have replaced the spark plugs, O2 sensors, had a smoke test done (no leaks found), eventually replaced the MAF, and cleaned the fuel injectors. The codes keep coming back as P0150 and P0174. I pulled the new spark plugs to have a look and the passanger side plugs are much dirtier than the driver side. I am at a loss.

 

Make sure your SAI filter is clean, there is a "how to" in the DII section.