My 190E 2.5-16 has a rattle at high rpm.. like 5000 rpm plus.

It's pretty loud and noticeable, and it's not really a noise that is in time with the engine (i.e. So I'm pretty confident it's not in the valvetrain or anything).

Does anyone have any suggestions or ideas to trace this? I suspect it may be an exhaust rattle but can't think how to verify this? The exhaust has just been tightened right through as it was apparently loose..

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190E's:
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
http://www.maylane.demon.co.uk/190esmall.jpghttp://www.maylane.demon.co.uk/190esmall2.jpg