Recently bought a fabia that pics and chooses when it boosts turbo is good no play or movement no oil in any boost pipes or vac lines actuator is free all vacs are connected properly when driving no boost let off the throttle and go again it will boost  only when at low rpm it doesn’t pick up unless I let off the thottle and go again anyone any ideas? 

Sticking VNT mechanism, vacuum pulls it open and a spring shuts it, worth checking.

Just took the manifold off the core veins are all free

You need to check for codes, this is starting to sound electrical.

No codes at all 

Vacuum leaks?

 None
one to the egr 

one to the ball 

one to the airbox 

one to the acctuator 

There's obviously something wrong Neil, you just have to find it, is the car standard or remapped?

 

The N75 vacuum control valve is the next suspect, what about the vacuum line to the brake servo and the tandem pump vacuum lines?

Edited 6 March, 20206 yr by sepulchrave

Reads like it is going into limp mode. Getting any stored error codes may help.