aidi a6 :- whining noise

hi all, hopefully someone will have an idea what this problem is.
i have an 1999 audi a6 2.5 tdi saloon. and all of a sudden its started
sounding like a sack of spanners. there is this whistling hissing kinda
noise especially when the clutch is depressed, the turbo i think is working
fine and this was new 14 months ago. now we did have some serious flooding
were i live in hull but was very careful i did not get water in the car. the
car drives the same as normal as not lost any power and had a full service 8
months ago
if any one as any ideas i would be very grateful
thanks
stef