Sounds very much like the exhaust manifold gasket is blowing. First step is to try and get a spanner on all the nuts to check that they're tight.
It goes when warm as the manifold expands slightly to seal the gap
You won't know until you replace that nut
Seriously, replace the nut and see where you go from there. There's no point worrying unduely until you've done that.
All manifold studs are tight. I went to remove the downpipe and found 1 nut missing, 1 nut spun loose (right at the other end of the thread) and the others weren't that tight. I removed the downpipe and inspected and felt the exhaust turbine and all seamed O.K, spun nice and smooth and only minimal side to side play.
I then started it up! It was loud and im not sure if this sounds normal or not. Please give me your opinions. Cheers.
Toby. http://youtu.be/6eFvmHOZ0Nw
Blowing from, more than likely, exhaust manifold gasket. It's not your turbo at fault so don't worry! Are all the manifold studs tight? Also, not bottomed out on rust so feels tight. Then check turbo to manifold is tight, and turbo to downpipe.
476bhp & 415ft lb @ 1.9bar Magic by Ryan! Gone, but never forgotten Now with a mk1.5 & a NHB EP3
Problem solved It was the exhaust manifold gasket as 1 stud had broken. I striped it all down and replaced 4 studs all the nuts and gaskets. She now runs sweet as a nut