Turbo Overboost p023400

Hi all, bought Audi A6 C7 2015 3.0 tdi CRT 2 months ago. On the way home glowplug light started flashing and car went into limp mode. Scanned at home p023400 turbo Overboost. Car already had Dpf cut out. 

I have:

Reconditioned actuator

Blanked off and disabled egr

disabled adblue

remapped to original -dpf, egr, adblue

reconditioned turbo

replaced MAP, MAF

air manifold flushed clean from soot

swirp flap replaced

throttle body replaced

.... after all above error still comes on and car go into limp, only noticed now coming on while engine cold/warming up while driving. Error clears every time car turn off/on but eventually comes back on when start from cold next time. I'm out of options, mechanic says maybe Ecu replace but reluctant to do, believes won't help. Suggested maybe open up turbo pressure upper threshold. 

I'm maybe making it up but feels like boost isn't working quite right, almost like lagging at first then overrevving 1-2 sec later. 

Help please! Thanks in advance. 

Edited November 20, 2025Nov 20 by DimiPom
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