Originally Posted by
mudski
My money is on a warped exhaust manifold. Quite common with these motors. Get a bright torch and check, if you can, around where the manifold meets the head and check for any soot spots. Just thought. Is the intercooler the factory one? If so, remove it and check it for leaks, as this is also another common issue, factory leaks on the intercooler. Oily residue on the core of the cooler is a good tell tale sign of a holed IC. The noise just could be the boost leaking out.