Its a 04 a4 tdi avant with 290k klm full service history from new im the 3rd owner,the turbo is whistling on accleration, is this good or bad?

..DIESEL ENGINES THE OIL PRESSURE SENSOR IS SCREWED INTO THE OIL FILTER HOUSING ASWELL.PRISE OUT THE CAPS,UNDO THE NUTS AND REMOVE THE PLASTIC COVER ON TOP OF ENGINE.REMOVE THE INSULATION BENEATH COVER (WHERE FITTED).DISCONNECT WIRING PLUG FROM SENSOR AND UNSCREW......BE PREPARED FOR OIL SPILLAGE.Hope this helps you out, Good luck

check your clutch and fly wheel and if it is a diesel with a turbo if you have a bit of black smoke look at that aswell most likely the clutch dual mass fly wheel

Do you have a sunroof? If yes, you may have a clogged drain tube from the sunroof.

GL,
Td

The cam followers are self adjusting,so an engine flushing agent and new oil (10/40 semi synthetic), should sort out the "tapping" noise,When the engine is hot run at 3500 revs for 30 secs to reset gaps

Check engine and gearbox mounts

both sounds like a pipe is off or has perished where the oil has leaked onto it ,oil leak could be feed or return pipe ??need to jack it up and have a good look

Here is a manual, but you have to purchase it:

http://shopping.msn.com/prices/audi-a4-service-manual-1-8l-turbo-2-8l-including-avant-and-quattro/itemid2373553/?itemtext=itemname:audi-a4-service-manual-1-8l-turbo-2-8l-including-avant-and-quattro

OK now what i am going to tell you, you need to listen to....
sounds like your turbo is on the way out and need to be repaired or replaced
if you continue driving the car the spool may snap and go into your motor and that will cost you a new motor
stop driving it...
if you need to don't push the car be soft
diesels are not a good car to push anyway
take it and get it fixed or you will be out of pocket for some time
i have had this happen here and it is not worth the damage

leave it to a specialest or maindealer