I have one GFB Blow Off Valve for sale, it is currently fitted to my car. It looks exactly the same as the one in the pic below but mine is blue instead of red.
Works perfectly, excellent condition (one minor rub mark about 2mm diameter on the blue anodised section), quite loud when venting, adjustable spring preload on the piston. I also have the steel weld-on fitting to go with it (I never used it becuase my piping is aluminium).
Reason for selling: I am going back to plumb-back.
NOTE: will consider swap for similar style BOV in plumb-back type, as long as it is in the same good condition
Price: $100 + postage. Negotiable. COD or Pick-up only