'03 A4 Quattro Wierd noise/problem?
 

Running basically stock setup '03 A4 quattro with brand new turbo/clutch and car has been well kept, but I recently noticed this may be something just wearing out or i may just be a moron, but upon a hard (not launch) but acceleration on the throttle i'll notice what sounds like a quite loud straining noise or semi slipping (both with ESP engaged and disengaged) , now i dont know if this has anything to do with Quattro's central lsd mechanism or not, or possibly its wearing out, but please if you know anything inform me.
thanks!