mine has been doing this for past 5 months...
its only when the engine is cold, the jingling noise starts as the boost builds up and occurs in any gear, when I take the foot off the throttle the jingling slowly stops. As soon as the car has warmed up a bit and the temp gauge is half way then it i can no longer hear it..
i had my turbo off just over a month ago when jkm fitted the forge actutor and the chap there said it looked in good nik, so I am thinking its something else
i read djhorace's post about the rs4 fuel job fixing it, so I got one just not fitted it yet so will update once its on