Mathieu,
It is very difficult to describe a sound accurately via email but it is normal for this valve to make a metalic sound during actuation, we also have another valve that uses a vary similar valve body and flange that makes the sound. The sound can be increase if there is a vacuum leak from the top of the valve, check to make sure that this isn't the case.
Patrick Robles
www.forgemotorsport.com
Tel: 407.447.5363
Fax: 407.447.5361
does anyone know where to get the forge recirculate valve and how much?