Sounds like a farting duck

Same as I posted on fb, when I'm on and of the throttle between 2000-3000 revs
It makes a weird sort of duck noise (don't know how else to describe it) I'm hoping its the exhaust as I'm going to replace it and it just means I get to do it sooner than I was planning :smile:
but I'm not so sure I thought the noise was coming from the rear but after messing today it's coming more
from the front, it's driving fine and there's no warning lights someone mentioned to check breather oil separator on the inlet mani but I'm not sure what that is
 
its the oil separator on the inlet manifold...been a few with the same fault - its the black round disc with a rubber hose coming off it to the cylinder head...
 
Cheers, what I'm looking for to see if it has ant cracks;/ also popped too rstunning on way home they reckon its the
mani cat just what I need maybe it's sports cat time