I am also having the same issue. Bulbs light up, then shut off immediately. They will not remain on until after I switch them on/off about 3 or 4 times. Seller says that Nissan uses 2-3 different type of ballasts and that the bulbs he sells will not work with mine....
I honestly don't think Nissan uses different parts from one Z34 to another, but oh well..still waiting to hear from him