Why not check the turbo first, like I said it could be a crack in egr pipe or in the downpipe that's causing the noise. Check out the video at the bottom of this link
http://www.myturbodiesel.com/1000q/multi/boost-leak-tester-DIY-check.htm
and that's a leak, nothing wrong with the turbo.
http://www.myturbodiesel.com/1000q/multi/boost-leak-tester-DIY-check.htm
and that's a leak, nothing wrong with the turbo.