Knocking / Clunking sound from Rear of my E53

[DrunkenNinja]

My previous mechanic said that my exhaust manifold would need changing after my last service cause he spotted a hole. When he test drove it after a full service he said he heard a noise from coming from the rear that confirmed the problem. (funny thing was it wasn't making the noise before I took it to him) needless to say he is no longer my mechanic, he was way over priced for an indy anyway and this time hit me with a huge bill when giving my X back to me broken in my eyes.

This problem seems to get worse lately and the noise is starting to drive me CrAzY!!! Whenever I start up in the morning for at least the first 5 minutes I get this clunking sound, it is not related to acceleration or driving over any bumps, it is just there and the sound does not appear connected to the any movement being made at the time, the sound is random with no rhythm.

The problem seems more evident when the car is cold, but it can happen at anytime. My new mechanic just took the X an MOT and it passed with flying colours and the mecanic said he could not see a problem and that it was in great condition, I was hoping he would hear the noise but he didn't.

I explained to him about the Manifold and he said it's possible that this is the problem but it was nothing to worry about and not dangerous.

I did have a blown Turbo, not long before I took to the old mechanic for the service, I wonder if this is when the problem was caused?