Mechanical failure N249

[L100UEB]

Hello

I’m having an issue with my cupra r.
The issue is the car is over boosting
Plugged it in and it’s coming up with N249 mechanical failure we erased the code and drove around whilst it was plugged in the code soon come back.

I tried to do a by pass with a 3mm vacuum hose from the DV to the mani and left the N249 plugged in. Not sure if that’s how it’s supposed to be done but it still wasn't boosting right. So put it all back.
I can boost normally up to around 2.5 k revs and then it over boosts.

The car is stage 1 with all the supporting mods ready for stage 2 but this issue needs to be fixed before hand. Just hoping someone might of had the same issue or any new suggestions.

I have replaced and tested the DV!

 

[mty12345]

I can't see any obvious way that the N249 could produce an overboost condition at 2.5k. I guess if there was a big leak it could cause the DV to fail to open between gear changes, but if you are geting overboost under acceleration, then i'd check the n75 and the vac lines to and from it.