i got WDB along with this type of wastegate already installed. at first i wasn't pretty sure of its functionality but i did some revisions (thanx wikipedia and other associated pages). it is used to regulate the maximum boost pressure in turbocharger system. hehe by defining in english, it is a valve which controls the pressure limit before entering the engine for combustion.
however nothing lasts forever rite? the valve (spring rate) didn't functions effectively anymore as i went boosting until 2bar before the intercooler piping which connected to the throttle body got loose. well it's time to upgrade for tial mvs 38mm i guess hehehe. good bye Nitto!