Quick update after 6 days motoring with the Volant fitted (320 miles covered).
Well it's pretty quiet all round, cant hear much induction roar on WOT (think the exhaust drowns it out), I have noticed it makes some slight "breathing" noises at part throttle and when in low gear and building revs and backing off you can hear the hiss (from the DV I presume), and occasionally you can hear a chattering but nothing too shouty/gurgly like the ITG's on facetube
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Just fitted the engine cover today after some basic trimming (still needs tidying up, smoothing and painting yet) and you will need to trim off a little off the back right hand corner because of the thickness of the intake pipe, but no clearance problems other than that.