Remove the engine cover, and follow the pipe from the airfilter/maf (tip) there will be a 1" diameter pipe from the metal pipe at the top, that goes to a black cicular 90* valve. with a 5mm small rubber hose going to the top of it. that then goes into the TIP. this is the DV. remove it and look for tears in the diaphragm, and double check it operates by pushing it in and making sure it returns. or you could replace it with a Forge 007p.