im new to european cars, i been into hondas for a long time and decided to to get an audi, so i bought an a4 from the orginal owner (66 yr old lady) she had over 12k in maintnance receipts....anyways about a month after buying the car it devoloped a knock/tick sound, kinda sounds like a diesel. The sound goes away after i hit 1500 rpms and when the car completely warms up it is very faint even not noticable at times, also if the car is in nuetral it is less faint than in park or in drive..........any help would be great, just from doing my own research ive found maybe it would be the cam chain tensioner?
also i know my turbo is going out it smokes when i first start it for a few seconds and thats it, could that be the noise???

 

also while i really want to fix the problem i still need to drive the car daily, so i have put about 1500 miles on teh car with the sound and it hasnt got any worse, also i have no loss in power

 

I also have the same problem and trying to figure it out.