Hello,

I have overboost problem on my 1.9 tdi AHF engine.

VNT actuator moves freely, not sticking
VNT actuator starts moving at -3 inHg, stops at -18 inHg
Vacuum pipes checked, no leaks
Vacuum pump produces -30 inHg vacuum

On first 3 WOT pulls it overboosts from 2500 rpm to 4000 rpm, could be more, but I didn't want to risk for turbo damge. Then after 3 WOT pulls, turbo boosts normally and doesn't overboost until I restarted engine. Then I restart engine, overboost problem comes back.

What can cause this problem?
Tried a lot of things, nothing helped... Tried to switch n75 valve with n18, still the same....

Thank you.

Btw, I had upgraded turbo to GT1749VA from VNT15

Hello, It could be any issue with VNT actuator, VNT rod adjust or map adjust.

see the parameters of the boost diagnosis and compare with the real

Post some logs