S3 - no turbo after 4000 rpm

[capetos3]

Hello
I'm starting a new thread , because I couldn't find a solution to my problem.
The car is s3 8l APY 209 HP. Recently , the turbo actuator was changed and the car is running and driving great. The turbo is making 1 bar of pressure , but only up to 4000 rpm and then the boost meter starts to read 0. The drop in the pressure is sudden and it doesn't hold any pressure. Since I've got the car , there was an issue with the actuator and before the change , the car was only making boost from 4000 rpm up to 6000 and it was making a peak of 0.6 bars. The n75 valve was checked and it is working . I've also tried with another working n75. While adjusting the actuator , the car was tested and the first time it peaked at 0.8 bars and the issue was present then as well , which is leading me to think that it's not an overboost issue.
Thanks in advance for the comments!

 

[S3AMJ]

Done a smoke test to see if you’ve got any boost leaks?


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[capetos3]

I've checked all the piping and there seems to be no leaks . A smoke test has not been done.

 

[danny_dj3]

faulty divertor maybe? would defo go get a smoke test done tho, checking the piping by eye aint really going to be 100% acurate as it only take a hairline split to open up and all that boost is gone.

plus double check all hose clamps are tight

 

[<tuffty/>]

Fault codes?

<tuffty/>

 

[capetos3]

The only fault code is for the secondary air injection (P0411) .

 

[capetos3]

UP!
Haven't got time to test stuff on the car and I've been driving it as is. If anyone has any ideas, please reply. There is no change in the situation, the car goes out of boost after 4k rpm.
Testes with known working N75 as well as airflow meter.
Regards,
Alex