Damn rattles!
 

So I have the usual heat-shield rattle on overrun from 3500 revs downwards. Not so much of a problem. But I had a new one this morning and am kind of worried as it doesn't sound good. Best way I can describe it is if you put a marble in a cup and make it roll around the outer edge if that makes sense... with a metallic tingle to it.

I did a quick search but nothing definitive came up. It happens around 3500 revs in 5th and stops around 4000. Had it slightly in 2nd but couldn't replicate it in others. Sitting in the drivers seat I'd say it was coming from the left side of the engine, car was driving normally and boosting fine. Just worried that something is about to break clean off.. anyone experienced similar?