A170 Cdi injector problem?

[Tango]

Hi all,

I have a 02 A170CDi which is very noisy on idle, sounds like a tractor. Its been like this for approx 6mths but hasnt got worse just sounds the same. Are injectors a common problem for these cars if so, how much do Merc dealers charge for new injectors (parts only)

or could it possibly be the diesel pump??

Thanks.