I'm chasing a P0171 code (running lean) and after much research it sounds like a vacuum leak. I've searched the forum and I am just trying to verify the operation of the pressure regulating valve (black puck at rear of valve cover. I removed the valve and can blow air threw both connection pipes??? is this normal. when I look inside one of the pipes I can see a spring but it does not seem to serve a purpose. Has anyone figured this crazy valve out??? 2004 1.8T quottro

 

Well I bought the part $62.00 fro VW dealer and installed it. Technician at audi said this part will give P0171 and misfire codes. This part manages the turbo pressure boost. I cut it in half and the diaphram was rock hard. Attached are picures