it's located at the rear right of the engine cover nearby the airbox, and is a plastic part inbetween a vacuum hose from the TB and the engine cover.
arrowed in the pic
theres this rubber seal adapter in the engine cover bit that the valve plugs into (similar to a garden hose ya know?). remove the vacuum hose then carefully pull out the valve, should slip out eventually.
if you have taken the hose off, you are causing a air leak, which is air entering the engine without be recorded by the TB, put the pipe back on and it will be ok