@ Robski
I dont know exactly what you mean, but I think you mean the opening is done by pressure, the electric makes it possible to create pressure by closing the circuit in the injector.

My English is not so good (working on it), that's wy I don't explain everything in detail.

Yes it was a PD engine, but the camshaft does not open the injectors. The camshaft only pressures the injector. The actual opening is done electrical, just like a common rail.

Fuel check is a good one! An advise, check the injector leakback at cold and warm engine. Sometimes the injector starts leaking when it's warm. Also I had a seat altea in the workshop last week. The car was running on 3 - 3.5 cilinders during acceleration. At constant rpm it runs not perfect but not...

Can you check the boost pressure and egr feedback from 1000 to 3000 rpm?

The number 4 injector is getting a lot of extra fuel. Have you checked the leakback of the injectors?
As far as I know the temp. sensor in the exhaust is used to see if the regeneration tempature is reached.

As far as i know there is no option for this. I use a self made trigger button, connected to the 12 volt plug. The only problem might be that there are only 3 channels left when using a trigger button.

Looks like everything is okay after you cleaned the injectors. The only problem is your scanner confusing you

What are the values from the 4 gas test? I think the scanner is not correct. Most scanners have a function to give information from the lambda sensor in text, this value changes constantly from rich to lean. I think you see these values but the scanner puts them onder the open/closed loop function. ...

Do you have any dtc's?
You can take a look at the fuel trims to see how much and in wich way the adaption is out of range.
What's the frequentie from the lambda signal and is the signal high time the same as the signal low time?

Do you have any fault codes?
And have you replaced the spark plugs?