Do I normally travel at 110? Ummm ofcourse....
So let me paint a picture:
Travelling on flat ground, 110 km/h at around 2200 rpm. Boost is around 6-9psi...
Noise is heard and boost spikes to maximum for a few seconds...
Noise goes away and boost returns to normal range.
Driving under 2000 rpm, noise is not heard nor boost spiking.
As mentioned by TOYZX, the stepper motor could be playing games and on its way out but would it make the noise? Is that what allows pressure to build and the ECU then dumps the excess through the EGR? I have seen these for around $400... are they easy to bolt on? I have not really looked that far yet.
I am happy to fix parts that could be farked but genuinely seeking info as to what this problem can be. Surely I am not the first?