Metallic buzzing

[MikeyB82]

Since I bought my MK III GTi, there has been a loud, metallic buzzing audible in the cabin coming from the engine bay. Upon looking undernieth, and removing the CAT heatshield, (which Ive read can cause noise) it's still there.
The sound seems to be coming from the exhaust system, round about the manifold area, and its only heard when accelerating.

Anyone got any ideas or experience with this problem?

Cheers.

[Uruk Hai]

I don't know if its the same on a MK3 but I had this on my MK2 16V and it turned out to be a heat shield thats just at the bottom of the bulk head where the down pipe meets the center section, I just put a big jubilee clip around the shield and exhaust and did it up tight, job done 

[MikeyB82]

Yeah, I saw a piece of metal there, held on with one clip, but even after removing it, the noise is still present.
Almost sounds like an original VW Beetle when accelerating.