I don't think whether or not you can hear the turbo has much relationship to whether it is ok or not. Now if there is a pressure leak you will probably hear it more and be down on power.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Search here for a tute on how to set your valves. This is one of the very important maintenance deals with these cars, as they actually get tighter when they haven't been set for a long time. Then with the valves well set, and a fresh oil/filter change, (about 7 liters of diesel rated oil) take her out and give her a real good push . I predict that she'll dump a bunch of old soot and come home running much better. My CD sure did!
Actually while you are setting valves you can measure the chain stretch on your timing chain, (again do a search here)
Good luck

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Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR