GFB have a few model of BOV in M'sia market here, commonly the GFB Basic, GFB Bovus Maximus and GFB Stealth FX
Something special on Stealh FX is that, by utilising a unique air diverting system to send the vented air back to the inlet (rather than muffling it), there is no restriction and the valve still operates at maximum efficiency. For cars with sensitive air flow meters (AFAIK, Mitsubishi engine have this problem), the valve can be tuned to vent just enough air back to the inlet to prevent backfiring whilst giving the loudest possible blow-off noise.
Whereas for Bovus Maximus, it's the loudest of GFB range of BOV. I can personally show u how loud this Bovus can amplify from my L2 turbocharger.
GFB Basic leh.. no comment.. doesnt really have special characteristic. Due to its design of 5 hole pattern, this BOV ensures a huge venting area and free-flowing air path. Because of the free-flowing characteristics, this valve is not as loud as the Mach 1 or Bovus Maximus. This does however, make it a good choice for big horsepower engines.
For more information on GFB products, feel free to contact me @ maxis.2292130