Boost loss / noise when losing boost

[MK5GTIinside]

So recently my MK5 GTI 05 when i give it some it will start to hesitates could range from 40mph upto 80mph- a noise like a screaming cat stuck in the bonnet and loss of boost for a few seconds then comes back on boost the noise appears when it hesitates and doesn't boost for a few seconds anyone any ideas?

[Clarkj93]

Some possibilities that come to mind:
Diverter Valve - very common boost leak point for these engines, it's happened to most of us
Rocker cover gasket - less common but can be the cause, if it's really oily by the rocker cover seal then could be this

[mjmallia]

A split DV will make a louder than normal pssssst! noise, almost like a blow off valve.......no boost all the time, or at least very little with the car driving like a NA 2.0

Screaming or screeching......sounds like a turbo issue to me.....the blades hitting the walls of the housing.

[Fallout-NL]

Is the wastegate actuator ever known to cause issues like this on Mk5 GTI's?

I've recently replaced my DV, which improved the boost situation, but there's still times where I suspect I'm losing boost somewhere. Especially if I start accelerating from lower in the rev range, or at least, it seems that way.

[MK5GTIinside]

A split DV will make a louder than normal pssssst! noise, almost like a blow off valve.......no boost all the time, or at least very little with the car driving like a NA 2.0

Screaming or screeching......sounds like a turbo issue to me.....the blades hitting the walls of the housing.

Ye it sounds more like a screaming / screeching noise like you mentioned. more than any pssssst noise. may have to get it into a garage asap