I have read through quite a few posts regarding the testing of the N75 valve. Can anyone tell me how, if it is possible in the first place, to check the functionality of the N75 with vag? I have a persistent code (17964) and all the vacuum lines seem to be in good place. My question is, how can I tell if I have a bad N75 or not? What would the part number be for a 2002 Golf Auto TDI?