have you changed the downstream ones? I would just to rule them out, I know people say they dont do anything but I have been chasing a slight miss at idle changed them out and engine is finally running smooth.....also check your connections at the harness plug not the new sensor plug, the white plastic insert on my drivers side was loose so I had to pull it out and reseat it to ensure a proper fit and last make sure the rubber gasket on the o2 sensor(if it has one) isn't binding up causing a poor connection....

 

I had both 1171 and 1174 also. I did a lot of reading and found that most people fixed these codes had a Vacuum leak somewhere. 1 person had a leaking valve cover gasket, 1 had a bad injector o-ring and I had a leaking intake tube. I did a smoke test with a cigar and found that I had a vacuum leak where the intake tube connects to the throttle body. The clamp was on tight but the tube itself had worn down around the inside rim where is connects to the throttle body just enough that is wasn't making a good seal. I was able to wrap a piece of electric tape around the rim of the throttle body to seal it tight. I did another smoke test and there was no more leak. I cleared the code and it hasn't came back since.

Bottom line- Air is being sucked in somewhere past the MAF and you are running to lean.

Many people buy new O2 sensors trying to fix this code only to find out the same thing you did. In my opinion you have a vacuum leak. If you need help on how to doing a smoke test with a cigar let me know or you can check Youtube.

 

Here is the link to the thread I had going when I had the same codes:
https://landroverforums.com/forum/di...1-p1174-50352/

 

Yes I think I figured this puzzle out. Please see my other posting ugh more codes popped up need help. for the solution.