Just putting this here to see if anyone know anything about my problem, I bort the car in march before lock down during lockdown the car started juddering going up and down hills trying to cut out a little bit later it cut out and engine light came on said o2 sensor so got it switched light off no juddering car sweat after few days driving light came back on same thing but wont go off, a few people said could be ecu maybe need genuine Ford sensor fuel switch or pump just wanting to know if cheap easy fix and dont need engine or turbo need mot next month and ford dosnt know whats wrong with it 

I think from the few clues you have given that the problem is due to fuel starvation. I would drain the fuel tank, change the fuel filter and try ten litres of fresh fuel before panicking. It isn't likely to be the turbo and it is unlikely to be the engine. Repeated O2 sensor faults mean that the sensor is getting the wrong readings, not that it is necessarily faulty and the car is stuttering and down on power under load which is when the fuel demand will be greatest so it sounds as though it is not getting enough fuel.Your new O2 sensor will have forced the computer to learn the new calibration and so until it has calibrated, it would, most likely be putting in a bit more fuel. Now it has learned the characteristics of the new sensor, you are back where you started.  Most problems of this nature have simple causes - it is the correct diagnosis of them that is complicated!

I would start by asking questions. Does it start normally?

Does the engine idle?

Does the car accelerate when you push gently on the pedal?

Three yesses and you are looking at the fuel system and a blocked filter is a cheaper guess than a pump. 

I did a full filter change air filter well service but didn't put ford ones on the car put k+n on and changed oil to millers and then thats when o2 sensor started playing up it turns on fine auto start is fine it trys cutting out wile turned on I put foot down a little with revs and its good maybe it is fuel starvation but everythings fine 

Fuel filter? Oil level ok? not too high? Why did you put the K and N on? If everything is fine then you haven't a problem. Something is wrong and it appears that it is something you did. Put an ordinary air filter on, (The K and N is 90% probably making matters worse,) ensure that you haven't pulled any pipes off when putting the air filter on. Check this very thoroughly  and check that you have not overfilled the oil.You think everything is ok, but it isn't so you are unlikely to have checked your work. If you are out of your depth, take it to a local garage with a good reputation and ask them to investigate. You say Ford don't know. I doubt that. Did they work on the car or did you just ask for advice? If they did, what did they do? 

I took it too them and they did the full investigation of engine all recalls been done spark plugs all that said its ok it maybe the o2 sensor is all they said to purchase a genuine from them, but as I said to you same as them all the stuff was happening once I had it serviced from garage, they recommended the k n air filter oil filter from garage who fitted it they put 4.5 litres of oil in did spark plugs maybe ime using wrong oil maybe spark plugs not 100 percent but its been like this 6 months now drives fine on throttle accelerates at good speed dosnt miss a beat, like I said the ford garage in halifax just said change o2 sensor to there genuine one but didnt diagnose problem for causing the fault I dont want to spend money fixing problems if its not that 

Nothing wrong with car when I bort it I had a service done from garage who recommended the stuff they put on they also checked thoroughly and everything seems OK I also had an engine mount done becuase one was broke after the service and engine mount thats when problem started 

I cannot help you other than to say that you need to explain clearly to a professional what is wrong with the car and leave it to them. There is no free answer and you will need to pay what it costs to have it repaired.

Only had the problems since the service been told could need new ecu or change oil and filter see if that sorts it out 

Did you put the right oil in?

If it's throwing the light on then there should be codes stored, eliminate each fault per code and clear DTCs until you get to the problem.

It does sound like wrong oil, poor or insufficient fuel or it doesn't like the K&N