Hi,

I have just had a new engine fitted and at the same time put a bigger intercooler on it, upon driving it when the turbo is about to kick in it starts to sound like a balloon losing air. It doesn't do it when idleing and revving, just when driving.  All the pipes and hoses have been double checked and there doesn't seem to be anything else left to check. Any help would be greatly appreciated, thanks.

Edited 16 June, 201511 yr by NickWard

Despite what you say, when I saw the header, my first thought was of a pinhole leak in the HP intake.

 

VCDS can log boost, so you can see if you're actually getting what you expect.