Disco 2 new weird noise

Evening all. This is a strange one.
When coming off throttle at about 40-50mph I get a metallic vibration sound from the drivers side engine bay.like how you would imagine a metal pipe vibrating on a chassis to sound.it goes below 40.its not steering related and has only started on the last 100 miles and isn't overly loud.Seems to only happen when the engine has warmed up too.
The only work I've done before it started is change the sump.

Any ideas?

Foss

Check the ace pipes fixed to the chassis using a rubber block, just behind the driver side front wheel.

Dave

Ace fixings seem ok.I have just noticed when I wiggle my front exhaust pipe the flexi joint makes a grating noise inside the woven wire section...could be that on its way out I spose.no cat thankfully !