Right well our cossie has a boost issue now after 9Kmiles (SCS built)

Basically it's hunting up and down 200rev's, The dump valve make's a right sound when cold like (ppssstthh) but just on idle then once warm it's quiet but now it's started to make that sound warm,On idle and 50MPH without no boost and minimum acceleration!

Now when i increase boost slow it's fine but can't put it full on as the engine shudder's (like a restriction) The sound of the turbo is also then on an off (suction noise) The only thing i can think is the dump valve? But would it be possible?

Everything is new sensor's dump valve etc etc has only done 9Kmile's,

Plug's maybe?

Any help would be much appreciated

Just basic stuff to check etc. Or else mean's another drive over to harvey's.

CheeRS